Search Fire Behavior Field Reference Guide, PMS 437

Text (indexed):
  1. Visual Fire Behavior Descriptions
  2. Observing Flame Length vs. Flame Height
  3. Rate of Spread Estimator
  4. Fire Behavior Observation Reports

Visual Fire Behavior Descriptions

This guide identifies key terms for describing fire behavior and provides reference imagery and descriptive detail to aid observation reports.

Fire Observation/Description.

Observing Flame Length vs. Flame Height

Observing Flames, as proxy for fireline intensity and indicator of tactical limitations, requires careful observation of flame length versus flame height. It is also important to identify whether the observation is for head, flank, or back of the fire.

Flame Length: The distance measured from the average flame tip to the middle of the active flaming zone at the base of the fire. It is measured on a slant when the flames are tilted due to effects of wind and slope.

Flame Height: The average height of flames as measured vertically, up, and down. It is estimated by comparing the flame to a nearby object of known height. Flame height is needed to estimate spot distance from a burning pile.

Flame length is commonly estimated and referenced as analogous to the fireline intensity one would feel at the actively burning perimeter. Flame Height, on the other hand, is what most observers commonly report. Encourage users to identify and observe correctly.

Rate of Spread Estimator

From the NWCG Standards for Wildland Fire Module Operations, PMS 430.

Fireline observers can use this table to look up a spread rate based on how long it takes the flaming front to move a given distance.

Estimating Rate of Spread.

Fire Behavior Observation Reports

Fire Behavior Observation Form.


Text (indexed):
  1. What Makes a Good Analyst
  2. Selecting the Best Tool
  3. Basic Fire Behavior Tools
  4. Spatial Analysis Tools
  5. Online Resources

What Makes a Good Analyst (Mark Finney...FBSC YouTube Video)

Selecting the Best Tool

The fire spread and intensity models have been configured in a variety of forms to address fire potential in different temporal and spatial configurations. This table can help focus the assessment with the most helpful information.

How will the tool help answer your question?How will fire behavior change with the next big change in fire environment?
Sensitivity Analysis
Where will fire go today and how long will it take?
How will fire behavior vary across areas of interest during the burn period?
Where will fire go over several days given changing weather as well as fuel and terrain?What risk do identified values face over a given planning period?
Tool or Model
  • BehavePlus
  • Lookup Tables
  • Nomograms
  • Nomographs
  • Nexus
Short-Term Fire Behavior (STFB) or FlamMap Minimum Travel Time (MTT)  (Finney 2002).Near-Term Fire Behavior (NTFB) or FARSITE     (Finney 1998).
  • Fire Spread Probability (FSPro).
  • Uses Minimum Travel Time (MTT)  (Finney 2002).
Best Use, Calc TimeFirelineIncident/Event, 15 min to 1 hour.Incident Planning, 1 to 3 hours.Risk Assessment, 2 or more hours.
Forecast HorizonSingle PeriodUp to 3 days if weather persistent.Up to 6 days (evaluate forecast confidence).One week to 30 days.
WeatherSingle weather (wind and fuel moisture) scenario.Single weather (wind and fuel moisture) scenario over duration of run.Hourly, variable weather (wind and fuel moisture) over duration of run.Short term forecast plus ERC seasonal trend after that produce range of daily weather scenarios.
Gridded WindNoYes (WindNinja)NoNo
Max Spot Distance, Probability of Ignition.
Spotting Distance and Frequency
(one ember per node; spotting probability value higher than NTFB; start with .10% spotting probability).
Spotting Distance and Frequency
(16 embers per vertex; spotting probability value lower than STFB; start with .05%).
Yes (like STFB)
Principal Output(s)Not Spatial
  • Rate of Spread.
  • Flame Length.
  • Major flow paths and arrival times.
  • Perimeters.
  • Fire behavior grids.
  • Progression perimeters.
  • Probability contours.

Basic Fire Behavior Tools

Manual (Fireline) Methods:

Lookup Tables, Nomograms, and Nomographs are all direct implementations of the surface fire spread and spotting models and are constructed for use without computers.

  • Lookup Tables and Fire Behavior Nomograms are constructed for only the original 13 fuel models and represent only surface fire behavior. They provide simple means to estimate fire behavior on the fireline based on observed fine fuel moisture, fuel model, wind, and slope. They can be found in the Surface Fire Section, Surface Fire Behavior Lookup Tables.
  • Spotting Nomograms are for single torching trees only and do not account for terrain features. They can be found in Crown Fire Behavior Section, Spotting Fire Behavior.
  • Fire Behavior Nomographs, PMS 436-3, include only the 13 original fuel models.  Nomographs for Estimating Surface Fire Behavior Characteristics (Scott 2007) include both the 13 original fuel models (Anderson, 1982) and each of the additional 40 models implemented more recently (Scott and Burgan, 2001).

FLAME and the Campbell Prediction System are systems rooted in the concept that in the fire response to a fire, firefighters need to have a thought process that can help them identify what the fire is doing, how that relates to the fire environment (wind, slope, fire flammability), and what the upcoming changes will produce. Further, they focus on firefighter safety implications and encourage means of organizing thoughts for briefing firefighters.

While neither is in widespread use, they represent important attempts to blend the fire behavior prediction models and processes with fireline operations.

The Fireline Assessment Method, FLAME (Bishop, 2007) expects users to:

  1. Describe current fuels, winds, and terrain influences and the fire spread it is currently producing
  2. Identify what the Next Big Change will be during the burn period (slope reversal, fuel type change, forecasted change in the wind)
  3. Apply multipliers for windspeed, fuel, and slope to produce new estimates of fire spread to apply tactically.

Campbell Prediction System(CPS) identifies “three primary forces causing variations in fire behavior: wind slope and pre-heat.” It highlights the need to:

  1. Evaluate the specific “alignment of [these] forces” on each side of a fire and place on the landscape, and recognize the “fire signature, [or] the observed fire behavior” it produces.
  2. Identify “trigger points where a change in the alignment of forces will change the fire behavior [signature], creating either opportunity or danger.”


A desktop computer application that is composed of a collection of mathematical models that describe fire behavior, fire effects, and the fire environment based on specified fuel and moisture conditions. The program simulates rate of fire spread, spotting distance, scorch height, tree mortality, fuel moisture, wind adjustment factor, and many other fire behaviors and effects; it is commonly used to predict fire behavior in multiple situations.

Online Reference and Learning Resources

Due to periodic updating, users should check the Splash information found in the help menu to determine the version currently installed. Install the latest version. The latest version can be identified and downloaded from the BehavePlus Fire Modeling System website.

A collection of publications that support the BehavePlus Modeling System

A comprehensive set of training resources can be found at the BehavePlus online reference Tips and Reference Materials.  

An online self-paced course can be found among the self-study courses at the Frames Online Course System.

Creating a Workspace

To take full advantage of the BehavePlus system, users should consider recording their inputs, assumptions, and configurations within the BehavePlus file structure rather than on paper worksheets provided in the past. There are now enough options within the system that only knowing the fire environment inputs may not be sufficient to duplicate the results. Use these few guidelines to establish a BehavePlus Workspace and record all work, including documentation, by saving in the appropriate file format provided in the software.

In the BehavePlus File menu, the workspace submenu allows the user to open an existing workspace, create a new empty workspace, or clone the currently open workspace to a new location. The default workspace is located with the program files and is opened by default each time BehavePlus is opened.

Users should consider either creating a workspace on external storage (network folder or USB flash drive) or cloning the default workspace to one of those locations at the end of a work session when data files need to be shared, backed up, or archived.

There are individual folders for worksheet files, fuel model definition files, fuel moisture scenario files, individual run files that include system settings and modeling inputs, and unit settings. Work should be stored there.

Models and Tools Specific to BehavePlus

  • Two-Fuel Model Projection.
  • Special Case Fuel Models (Palmetto-Gallberry and Western Aspen).
  • The Tools Menu includes Units Converter, Relative Humidity estimator, Fine Dead Fuel Moisture (Fosberg) Estimator, Slope from Map Inputs estimator, and Sun-Moon Calendar.


NEXUS 2.1 is crown fire hazard analysis software that links separate models of surface and crown fire behavior to compute indices of relative crown fire potential. Use NEXUS to compare crown fire potential for different stands, and to compare the effects of alternative fuel treatments on crown fire potential. NEXUS includes several visual tools useful in understanding how surface and crown fire models interact.

The NEXUS2 installation file is nexus2.1.exe. Save this file to your machine and install from there; admin rights required. Alternatively, you may download the archive which contains the installation program plus the associated Readme.txt and ReleaseNotes.txt files.

Mobile Apps

Wildland Toolkit 

Spatial Analysis Tools

There are a number of different fire behavior analysis systems that incorporate different combinations of the models referenced here.  This a good guide to the different modeling systems, their inputs, and how they are used.

Scott, Joe H. 2012. Introduction to Wildfire Behavior Modeling. National Interagency Fuels, Fire, & Vegetation Technology Transfer.



Online Resources

Wildland Fire Decision Support System (WFDSS)

Interagency Fuels Treatment Decision Support System (IFTDSS)

Alaska Fire Weather and Fire Behavior Prediction Tool

Great Lakes Fire Weather and Fire Behavior Prediction Tool



Text (indexed):
  1. Reference Fire History
  2. Key Spatial Analysis Factors
  3. Evaluating and Adjusting Spatial Assessments

Reference Fire History

Wildland Fire Library 
Evaluate reference fire history and other local knowledge for insight into current fire situation.


The Wildland Fire Library website provides a wide range of historic fire assessment products defined by location and date.

Near Real-Time Remote Sensing Products

  • MODIS, VIIRS, GOES, and Firehawk IgPoint Fire Detections are available on the Enterprise Geospatial Portal (EGP), in WFDSS Situation and Analysis Maps, and from Google Earth tools.
  • National Infrared Operations (NIROPS) Interpreted Infrared Products may be produced to support incident specific needs.
  • Web-Cams and FLIR resources may be assigned to specific incidents, or in some cases, available publicly from airports and other locations.

Key Spatial Analysis Factors

Consider what analysis settings and inputs can be used to represent real factors influencing current and expected fire behavior.

Landscape (LCP) Characteristics

The fuel model and canopy selections provide important influences on all of the factors that follow. In some areas, default LANDFIRE data need evaluation primarily for recent changes (burn scars, other significant disturbances) and barrier depiction. In other cases, significant editing of fuel models and/or canopy characteristics may be needed to reflect seasonal changes and errors in classification.

Crown Fire Potential

If the landscape (and the analysis) present potential crown fire spread events, growth estimates need to reflect significantly different spread rates. As currently configured, the models present three different approaches for estimating crown fire growth and behavior:

  • In the spatial analysis tools, there is a choice between two different implementations of the Van Wagner transition model used to select surface, passive crown fire, or active crown fire for fire behavior estimation (Comparison Table). The Finney method, produces less active crown fire and models passive crown fire with the spotting model only. The Scott & Reinhardt method, produces more active crown fire and models an intermediate spread rate when passive crown fire is anticipated.
  • There are surface fuel models (generally in the shrub category) that have been touted and used to represent crown fire behavior.

Spotting Spread Potential

Estimating spread potential across barriers and from other random movements (e.g. rollout) generally requires a stochastic model that factors in frequency potential, or probability. The spotting models implemented in spatial analyses provide a frequency modeling of the firebrand production and movement as well as the likelihood for a new start.

Burn Period

The NWCG Fire Glossary defines the burn period as that part of each 24-hour period when fires spread most rapidly; typically from 1000 hours to sundown.

In most cases, the burn period refers to the period when fire is actively spreading at the head of the fire. If the six categories of visual fire behavior are considered, the 24-hour day includes all of them. Field Observers should be careful to report/describe their estimate of burn period accurately and purposefully and relate it to the type of fire observed:

  • Smoldering fire behavior continues around the clock for most active fires. It does not represent any part of an active burn period if reported at the head.
  • Creeping fire behavior may continue through the night, but is generally transitional between smoldering and running fire behavior. Generally, it produces little overall fire spread and is not considered part of the burn period if observed at the head of the fire.
  • Running and Torching/Spotting fire behavior describes what is encountered during the burn period on most days when fire spread and overall growth is low to moderate. However, it may represent transitional fire behavior when more significant Torching/Spotting or Crowning fire behavior occurs during peak hours.
  • On days when Active Crowning fire behavior is predominate, the burn period used for analysis should generally reflect only the period of significant spread.

Burn period can vary from day to day for a variety of reasons:

  • Solar Radiation heats fuels as well as warming the air and lowering relative humidity. These influences lower fuel moisture, creating conditions favorable for active burning. Affected by the sun angle based on the time of year and latitude. Cloud cover and canopy shading can further reduce solar radiation.
  • Fuel bed Characteristics can influence burn period as well. Moisture content of light fuels, such as grasses, respond more quickly to changes in temperature and humidity.
  • Diurnal Fuel Moisture Trends are affected by the quality of night time humidity recovery and inversions. Slope/aspect and recent precipitation all affect the length of the burning period for a given situation.
  • Drought can influence the length of the burn period through the heat produced in the burning of heavy fuels.
  • Direction of Spread can be an important factor as well. Backing spread can start later and end earlier in the day for a given situation.

In the validation of your estimate, there are tools and criteria that can help identify when the burn period starts and ends.

  • Fireline Observations are probably the first and most important source of information for determining the burn period. Try and get answers to specific questions as you pursue a reasonable estimate. When and where did fire begin to move and when did it slow down on previous days? Was there significant spread during the night? What were observed spread rates and when?

Sometimes these reports are incomplete and need to be correlated to other information as suggested below. FSPro seeks burn period information for different types of days. These factors suggest that fireline observations should be reinforced with these other information sources where possible.

  • Sunrise-Sunset Tables (time of year and latitude) from BehavePlus and solar radiation sensors can show periodicity and suggest timing of beginning and end of active spread.
  • Diurnal Wind, Weather and Fuel Moisture Trends can similarly show a periodicity that can suggest timing of active spread. Graphs displaying these trends are readily available at MesoWest.
  • Fire Progression Maps suggest the overall daily spread around the fire, and with knowledge of weather conditions, fuels, slope and spread direction, can be compared to modeled growth. A new resource called the Wildland Fire Library provides a variety of historical references including fire progression maps.

WFDSS Help suggests that “The default burn period in NTFB is 24 hours; however, modeling a fire overnight is generally not advised. NTFB, like FARSITE, has a tendency to over-predict overnight fire spread. For this reason, most analysts shorten the duration that the modeled fire is allowed to burn each day.”

Each fire growth projection, whether using non-spatial tools (BehavePlus) or spatial tools (WFDSS analyses NTFB and FSPro) specify a duration as the number of hours or minutes to obtain a resulting fire size and/or perimeter. Characterizing the duration as the number of hours or minutes in a day (burn period) for a projection allows the user to model growth for multiple days.

Burning Thresholds and Burn Day Frequency

Most of the area burned across any management unit, geographic area, or ecological region occur on relatively few days over the life of the fires that are included in them. Burn Day evaluation can help identify which days have conditions receptive to significant fire spread and can serve as indicators of important transitions in fire behavior.

The concept recognizes that there are thresholds in environmental conditions below which significant spread is substantially limited, even when fire spread models estimate that spread will continue. A simple classification of days into [Burn Days] and ‘non [Burn Days]’ can greatly improve estimates of area burned. (Podur and Wotton, 2011). There can be important within and between season variation in this pattern.

  • WFDSS FSPro analysis defines a threshold ERC for each analysis, below which no fire spread is modeled for the entire day. Among its outputs, a distribution of burn days spread across the ERC classes is provided. It is possible to define daily environmental conditions favorable to significant growth and use those to estimate the frequency with which they occur to adjust the default 60th percentile ERC as that threshold (Ziel, 2015).

FSPro Burn Day Summary. FSPro defines a threshold that defines the conditions for minimally active burn days based on ERC. With that definition, and its modeled time series, frequency of burn days and no burn days can be predicted.

  • WFDSS NTFB analysis requires input of a burn period for each of the included days. Specifying same start and end hour for a given day essentially defines it as a non-burn day. The same daily conditions mentioned for FSPro can be used as criteria to exclude specific days or adjust burn period in NTFB analyses.

 Each Near Term Fire Behavior (NTFB) analysis defines the burn period start and end time for all days in the analysis period.

Wind Speed and Direction

With a sparse network of RAWS stations that provide hourly reports, it may be difficult to find a weather station that represents both wind speeds and directions appropriately for the analysis. Review observations and forecasts carefully for both speeds and direction. Try analyses with alternatives being considered.

Weather Station climatology in FSPro analysis is generally restricted to RAWS installations. For that reason, many analysts choose a combination of 10-minute average and gust wind speeds in those climatological distributions. This results in approximately a 50% increase in wind speeds. ASOS/AWOS climatologies often reflect this higher wind speed. View wind roses for ASOS/AWOS stations. This difference is often found in NDFD forecast wind speeds as well. Consider a similar adjustment to 10-min RAWS winds when conducting calibration analyses in STFB and NTFB.

Weather Observations and Forecasts

In most cases, forecasts have difficulty outperforming climatology beyond 48-72 hours. Most important are confidence in wind and precipitation elements. Read the area forecast discussion for insight into the confidence horizon.

Extend STFB and NTFB analyses only to the limits of very high confidence, usually 1-3 days. FSPro Analyses combine forecast and climatology. Extend use of forecast inputs out beyond 3 days only if confidence for the extended forecast is unusually high. Critically examine the wind speed and direction in the forecast.

Dead Fuel Moistures

Fine dead fuel loading and moisture generally determine day-to-day variability in flammability in specific locations. Generally, fine fuel moistures are set by weather inputs. However, they may not reflect sufficient range in an analysis period to produce the observed variability. Evaluate landscape distribution in 1 hour and 10 hour fuel moistures using the Basic Outputs from Basic and STFB analyses. Consider the range of variability in these fuel moisture categories applied in the ERC table of FSPro analyses.

Live Fuel Moistures

Among all fuel moisture categories, live fuel moisture levels can have a dramatic influence on results in fuel models that include them. Among the original 13 fuel models, the most dramatic effect is in the shrub models FB04 and FB07. With the inclusion of the 40 Scott and Burgan fuel models, herbaceous (grass) and shrub live fuel loads have been included separately. With these, the most dramatic effects have been shifted to fuel models that include herbaceous fuel loads (Grass, Grass/Shrub, some Shrub and some Timber Understory).

In these fuel models with live fuels loads, herbaceous fuel moisture trends establish curing levels and transfer of herbaceous fuel loads to dead fine fuel loads.

  • Where curing is a critical cue to increasing fire potential, live fuel moisture levels can be set to simulate current conditions. New NFDRS tools for estimating live fuel moisture can be useful in setting current levels.
  • Where critical thresholds for active fire behavior can be reached in green landscapes with growing vegetation, NFDRS estimates generally produce high live fuel moistures. This usually overstates its influence as a heat sink and can confound modeling efforts. In these environments, default estimates are often adjusted downward in modeling efforts. Consider adjustments for only fuel models that represent fuel beds that are burning actively.

Evaluating and Adjusting Spatial Assessments

"You have to study, figure out what [the fire is] seeing and represent what is the fire seeing and how is it responding to the various factors in reality. And then can you replicate that for the right reasons with the model? Can you get pretty close to it? If you're not getting the right answer for the right reasons, I don't care how pretty your output is..." Mark Finney, Research Forester

Verification of Analysis Models

Verification is a demonstration that the modeling formalism is correct.

Though much of the verification work was completed in the development of a model, end users have a responsibility to evaluate large scale factors to ensure that the range of variability used produces the range in results that generally fit observed outcomes. Learning regional preferences and default analysis inputs are an important first step.

Consider the static factors applied to analyses:

  • Is crown fire an issue for this fire? What methods and spotting inputs are preferred in the region?
  • Are there standard landscape edits identified for the area?
  • How are slowly changing seasonal and drought factors typically represented there?

Analysis Adjustment and Calibration

Calibration is the estimation and adjustment of the model parameters and constants to improve the agreement between model output and a data set.

Persistence prediction estimates applied from observations in the recent past and comparison of inputs with forecast elements are the most common form of fire behavior calibration. They can be applied as spread event size, fireline intensity, and crown fire behavior, or as specific adjustments to input elements (e.g. local wind speed and direction).

Otherwise, careful evaluation of important input factors should allow the model to reflect the variation in conditions truly influencing the fire.

Calibration Input Factors to Consider (categories Bold,; edit locations in normal text):

VariabilityLarge ScaleMedium ScaleSmall Scale
Diurnal Changes (Primarily for NTFB, STFB)Burn Period length

(NTFB Info Tab-Burn Periods)

Wind Speed & Wind Direction, Cloud Cover, Precipitation

(NTFB Info Tab-weather summary)

1 hour (when over 24 hours in primarily grass landscapes)

(Info Tab-Initial Fuel Moistures, Conditioning Days)
1 hour (when over 24 hours in mixed forest, shrub and grass landscapes)

Info Tab-Initial Fuel Moistures, Conditioning Days
1 hour (if burn period only includes peak hours)

Info Tab-Initial Fuel Moistures, Conditioning Days)
Day-to-Day Variability STFB, NTFB, FSProWind Speed & Wind Direction

(STFB Info Tab, FSPro ERC Stream Tab- Forecast)

Burn Period length, Burn Day frequency

(FSPro ERC Classes Tab, NTFB Info Tab-burn periods, STFB Info Tab-Hours)
1 hour fuel moisture

(FSPro ERC Classes, NTFB & STFB Info Tab-Initial Fuel Moistures, Conditioning Days)
10 hours, 100 hours fuel moistures

(FSPRO ERC Classes Tab, STFB & NTFB Info Tab-Initial Fuel Moistures)
Seasonal Trends STFB, NTFB, FSProBurn Period Length, Burn Day frequency

(FSPro ERC Classes, NTFB Burn periods, STFB Hours)

Herbaceous Fuel Moisture

(FSPro ERC Classes, STFB& NTFB Info Tab-Initial Fuel Moistures)
Woody Fuel Moisture

(FSPro ERC Classes tab, NTFB or STFB Information tab: Initial Fuel Moistures, Conditioning Days Initial Fuel Moistures)
Fixed Fire Environment STFB, NTFB, FSProAnalysis Barriers, Crown Fire Method, Spotting Frequency

STFB/NTFB/FSPro Information Tab)

Fuel Model, Canopy Cover

(Landscape Editor Tab)

Terrain: Slope, Aspect, Elevation

Fixed, but review for problems/errors
Canopy Base Height, Canopy Bulk Density, Stand Height

(Landscape Editor Tab)

Steps to consider:

  • Consider including last known day within the forecast analysis for quick, embedded validation.
  • Edits to Large Scale Constants first.
    • Fuel Model & Canopy Layers can require local edits due to disturbance, classification errors, and possibly seasonal trends. These fuel characteristics can have a large impact on outputs. It is CRITICAL to account for things that will check or stop fire spread, so ensure that recent historical fires are reflected in the LCP. Also, make sure that rock and water are adequately mapped. However, other fuel layer adjustments should be considered only when the changes you contemplate are appropriate and will result in significant changes in fire growth. Otherwise, edits may mask necessary variability.
    • Barriers are critical factors in anticipating fire growth.
    • Crown Fire Method and Spotting Frequency are frequently settings applied consistently with experience in particular landscapes. As these become standard, they become verified.
  • Edits to seasonal factors as well as medium and large scale Day-to-Day factors.
    • Burn Period Length and Burning Threshold edits should be consistently applied according to seasonally changing day length, in view of drought assessments, and according to daily variability when limiting burn period.
    • In most situations, Herbaceous and Woody Fuel Moisture trends should reflect reasonable ranges for season, drought and curing levels. Where active fire is anticipated in green growing landscapes, it may be best to identify fuel beds that are most prone to active burning and edit live fuel moisture specifically for those fuel models.
  • Edits to diurnal weather-related inputs (temp, rh, wind speed/dir, cloud cover) should be limited to standard kinds of adjustments to preserve relevance of observed calibrations to forecast projections.
    • Wind Speed and Direction is most important factor. Ensure that observed portion of weather stream reflects observed fire spread and that winds observations are appropriate for situation. Precipitation estimate may not represent fireline amounts. Consider adjustments carefully.
  • Calibration may require a couple iterations.
    • Do not over-calibrate to over fit the result.

Validating Spatial Analyses

Validation is a demonstration that a model, within its domain of applicability, possesses a satisfactory range of accuracy consistent with the intended application of the model.

Validation is used to evaluate forecast projections from applied calibration adjustments. Here are some methods and some considerations:

To determine if analysis prediction should be accepted/completed:

  1. In any validation effort, evaluate weather forecast first to frame consideration of analysis prediction results.
    • Compare winds, cloud cover, and precipitation in the analysis forecast to other forecasts you are using.
    • Check forecast portion of ERC Streams in FSPro. Are the number of days appropriate? Are the wind forecasts reasonable?
    • Is the analysis duration appropriate with the given forecast confidence for STFB and NTFB?
  2. Evaluate ignition locations/sizes and barrier locations for appropriateness. They may be too large or insufficient.
  3. Compare analysis inputs and adjustments from the analysis (using the table above) to known factors influencing fire growth and behavior.
    • Review notes in each tab for the analysis to determine what adjustments were made and why.
  4. Critique the results. Are they surprising? Are they useful? How will you brief them? Judgment and experience are important.
    • FSPro: The Big Red Cloud and the Small Rare Event.
    • NTFB/FARSITE: Review Other Characteristics (flame length, spread rate, crown fire activity) for reasonableness.
    • STFB/FLAMMAP MTT: Look at Basic Outputs.
  5. Document your conclusions in the analysis notes.

When analyses need updating or have expired:

  1. Compare weather forecast or climatology in the analysis to observed weather to determine how that influenced analysis accuracy.
  2. Compare subsequent observed perimeters with predicted perimeters and flow paths for the concluding date of the analysis period. In FSPro, there may be benefit to comparing both the concluding observed perimeter and the observed perimeter at the date where the forecast stream concludes.
    • Do predicted perimeters and flow paths for STFB and NTFB represent actual spread directions and produce a reasonable representation of the size of observed spread event?
    • Does NTFB predictions reflect day-to-day variability effectively?
    • Did the probability contours in FSPro provide useful insight for contemplated strategies and priorities for planned actions?
    • Does the analysis effectively represent fire behavior observed over the period (surface, spotting, and crown fire behavior)?
  3. Critique levels and adjustments to inputs factors that relate most closely to real influences and variations seen over the analysis period.
    • Check Ignition and barrier files. Are they responsible for significant differences?
    • Evaluate burn periods, burning thresholds and burn day frequencies to develop a sense of day-to-day and diurnal variability in the analysis and on the ground.
    • Are the seasonal factors effectively representing observed departures from normal levels?
  4. Update Analysis notes with the evaluation.
Text (indexed):
  1. Briefing Guidelines and Products
  2. Analysis Notes
  3. Risk Assessments and Management Decisions
  4. Incident Narratives
  5. Documentation Records

Briefing Guidelines and Products

Fireline Briefing Checklist (Situation)

  • Fire name, location, map orientation, and other incidents in the area.
  • Terrain influences.
  • Fuel Types and conditions.
  • Fire Weather (previous, current, and expected) including changes in winds, temperature, RH, cloud cover, and significant events.
  • Fire Behavior (previous, current, and expected) times and thresholds for active behavior, significant spread, and flame length issues.

Fire Behavior Forecast

Incident Briefing Outline

Analysis Notes

Identify and explain the key inputs and assumptions that frame the analysis, highlight the primary conclusions, and describe the limitations and uncertainty that limit your confidence in the information provided.

WFDSS analyses allow the analyst to associate Notes sections with every input section of the analysis and in support of the final disposition (accept/reject). However, even informal briefings should document the basic assumptions, the expected fire behavior, and the implication for management decisions.

Risk Assessments and Management Decisions

The primary reason for conducting fire behavior assessments is to support decisions. Decisions occur in an environment of uncertainty, and involves choosing a level of risk to avoid, to mitigate, and to accept. All Incidents in WFDSS provide for maintaining an updated Relative Risk Assessment and a dependent Organization Assessment. Both are shown here.

Relative Risk Assessments

In WFDSS, relative risk assessments include three primary considerations:

  • A Probability Assessment from Time of Season, the barriers to fire spread, and current/expected seasonal severity.
  • A Hazard Analysis from fuel condition, current fire behavior, and potential fire growth.
  • An assessment of Values at Risk based on fires proximity and threat values, identification of cultural and natural values, and Social/Economic concerns.

WFDSS Relative Risk Assessment: Subjective assessments of Hazard, Probability, and Values are integrated objectively into an overall characterization of incident risk.

Organization Assessments

These include the relative risk assessment, an evaluation of difficulty implementing the incident strategy, and a factor for the socio/political concerns for the incident and the values at risk.

WFDSS Organization Assessment. Similar in format to relative risk assessment (above), it incorporates many factors into a recommendation about fire management organization needs.

Extended Risk Assessments

Provide additional justification and validation of the decisions and actions associated with Management Action Points, resource allocations by Geographic Areas (GA), Management Area Coordination (MAC) groups, and individual agencies. They should reinforce the relative risk and organization assessments mentioned above.

Though organization of the document is flexible, consider the elements in the relative risk assessment to ensure that this supporting document provides a focused collection of products, processes, and analyses that organizes information and assigns ratings to inform priorities and courses of action for decision-makers. An outline might include:

  • An enumeration of values at risk.
  • Reference Fuels, Climatology and Fire Behavior/Growth history as base line for current situation.
  • A description of the current situation as it differs significantly from the reference conditions above.
  • Expected fire behavior and growth based on analysis and judgment. Include statement of assumptions, limitations, and uncertainty in the analysis.
  • Anticipated impacts and effects based on the fire analysis.
  • Conclusions in support of the relative risk assessment.

Review and Update

Relative/Extended Risk, Organization, and Allocation assessments should be reviewed and updated where:

  • The fire has spread outside the planning area or outside the contours of the FSPro analysis used in the assessment.
  • The planning area is expanded.
  • Unexpected fire behavior is observed on the incident.
  • There weather forecast and outlook basis used in the assessment have changed significantly or expired.
  • The analysis horizon for the fire behavior outputs has expired.

Incident Narratives

The fire behavior narrative is an important document that captures key fire behavior information for the incident. It is often summarized (executive summary) for the final incident package. It is a dynamic document that is driven by the incident, the fire behavior, and analyses performed. It is a standard component of a fire behavior documentation package.

This may include representative RAWS sites, assumptions/limitations specific to the incident, local observations, or other relevant information that assisted with your analysis and interpretation.

While it does not have a specific format / template, there are elements common to most fires. An example is shown here:

  • Heading with Incident Name, Period of Record, and Author.
  • Fire Weather/Climatology.
  • Fuels and Fire Danger.
  • Fire Behavior.
  • Significant Analysis.
  • Chronology of Fire Behavior Events.

Documentation Records

Fire Behavior Documentation Package

  • Fire Behavior inputs and outputs specific to BehavePlus or model used.
    • Worksheets (completely filled out with times and dates).
    • Assumptions.
    • Index of runs and names.
  • Maps (labeled with dates and times).
    • Fire spread projections.
    • Fuel model.
    • Points of concern/values at risk/MMAs/M.A.P.s.
  • Unit logs (ICS 214).
  • Outline of information provided in briefings.
  • Fire behavior forecasts (validated) and any updates or supplements.
    • Document actual conditions and fire activity.
  • Specific events (with time frames).
    • Change from wildland fire use to wildfire; time frames.
    • Significant events.
    • Unforecasted weather events and resulting impacts on fire behavior.
    • Special or specific operational plans.
    • Special prescriptions.
    • Long range forecasts.
  • Reference materials used during the assignment.
  • Sources of data and why particular data sets were used or not used.
  • Risks assessed and why, and what the consequences may be.
  • Notification (who/when/how) of changes in predictions.
  • Fire Behavior Chronology and Narrative.

The package needs to support and describe the rationale behind your recommendations and explain how you choose to deal with conflicting information. All information needs to have the incident name, date/time, your name, and any other pertinent information on it. All documents need to be in a format the can be preserved as required by national documentation standards.

Electronic Fire Behavior Documentation

Any or all of the Fire Behavior Documentation may be produced and submitted in electronic format.

  • Ensure, if the documentation is a mix of paper and electronic records, that the file naming conventions are consistent and that they are organized in a meaningful way.
  • File formats are becoming less proprietary, but make sure that the format is in a common format and readily readable by other users and their computers. Highly formatted documents should be saved in PDF format as well as in the original.
  • Document desktop software name, vendor, and version. Consider including the install file.
  • Integrate files into the incident digital record and keep a copy of your submissions.
Text (indexed):

Fire Assessment References

Bishop, Jim, Technical background of the FireLine Assessment MEthod (FLAME), U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, 2007.

Finney, M. A.,  FARSITE: Fire Area Simulator—model development and evaluation, U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, 1998.

Finney, Mark A., An Overview of FlamMap Fire Modeling Capabilities,  U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, 2006.

Finney, M.A., Grenfell, I.C., McHugh, C.W. et al., A Method for Ensemble Wildland Fire Simulation. Environ Model Assess, 2011.

Heinsch, Faith Ann; Andrews, Patricia L., BehavePlus fire modeling system, version 5.0: Design and Features, U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, 2010.

Podur, Justin and Wotton B. Mike, Defining fire spread event days for fire-growth modelling, International Journal of Wildland Fire, 2011.

Pontius Jr., R.G., Huffaker, D., Denman, Useful techniques of validation for spatially explicit land-change models, Ecological Modeling, 2004.

Rothermel, R. C., How to predict the spread and intensity of forest and range fires,  U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station, 1983.

Rykiel Jr, E.J., Testing ecological models: the meaning of validations, Ecological Modeling, 1996.

Scott, Joe H. and Reinhardt, Elizabeth D., Assessing crown fire potential by linking models of surface and crown fire behavior, U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, 2001.

Scott, Joe H.,  Introduction to Wildfire Behavior Modeling, National Interagency Fuels, Fire, & Vegetation Technology Transfer, 2012.

Stratton, Richard D., Guidance on spatial wildland fire analysis: models, tools, and techniques, U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, 2006.

Stratton, Richard D., Guidebook on LANDFIRE fuels data acquisition, critique, modification, maintenance, and model calibration,  U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, 2009.

Text (indexed):
  1. General References
  2. 78/88 Version NFDRS Structure
  3. 2016 Version NFDRS Structure
  4. NFDRS Version Comparison

General References

Fire Danger ratings are an effective part of daily risk rating and operational preparedness for fire management agencies across the world. Chapter 10 – Preparedness of the Interagency Standards for Fire and Fire Aviation Operations outlines processes and resources applied in the development of standard Fire Danger Operating Plans in the United States.

Included in Fire Danger Operating Plans are:

  • Specification of fire danger ratings.
  • Identification of climatological thresholds for administrative purposes. Default thresholds include the 90th and 97th percentile values for key indices in the applied system. The Bureau of Land Management (Department of Interior) uses the 80th and 95th percentiles instead.
  • Communication of those danger ratings, including both internal and external forms.

Some valuable links:

A variety of fire weather systems are applied in danger rating around the United States. There are primarily two systems used in fire danger operating plans.

U.S. National Fire Danger Rating System (NFDRS):

First introduced in 1964, NFDRS has been updated in 1972, 1978, 1988, and now 2016 to integrate newer science and improved processing. This guide will compare important aspects of the 1978, 1988, and 2016 versions, detail important outputs, and describe primary components and indices. More information about the system and the latest update to it can be found at:

NFDRS 2016 Information Page

NWCG Fire Danger Subcommittee Website

The Canadian Forest Fire Danger Rating System (CFFDRS) Fire Weather Index (FWI) System

CFFDRS was introduced in Canada in 1970. Implemented in Alaska and the lake states of Michigan, Minnesota, and Wisconsin in the early 1990's. Details about CFFDRS are included a separate section of this guide. The following websites provide data access:

Other tools, formulations, and applications are used locally across the country. Some examples are highlighted later, in the Fire Danger References Section.

78/88 Version NFDRS Structure

 Structure and Process Flow of the 78/88 National Fire Danger Rating System.

2016 Version NFDRS Structure

Structure and Process Flow of the 2016 National Fire Danger Rating System.

NFDRS Version Comparison

Category78 Version88 Version2016 Version
Fuel Models and Settings
  • 20 NFDRS specific fuel models
  • Grass identified as annual or perennial
  • Shrub type not detailed
  • Specific revisions to 3 of the 78
  • Version fuel models (C, E, and N)
  • Grass identified as annual or perennial
  • Shrubs identified as evergreen or deciduous
  • Reduction to five new 2016 Version NFDRS specific fuel models (V, W, X, Y, Z)
  • Grass identified as annual or perennial
  • Shrub type not detailed
Climate Class
  • Used to determine dormant 100 hours, 1000 hours, and live fuel moistures
  • Used to specify duration of green-up process and influence curing rates
  • Used to determine dormant 100 hour, 1000 hour, and live fuel moistures
  • Station Catalog identifies location as Humid with on/off toggle. Influences Max SC and Moisture of Extinction
Manual Inputs
  • Observation type
  • Snow Flag
  • Wet Fuel Flag
  • Green-up/Freeze Flag
  • State of the Weather
  • Observation type
  • Snow Flag
  • Wet Fuel Flag
  • Season
  • 1 hour = 10 hour?
  • Daily Herb & Woody Greenness Factor
  • State of the Weather
  • Snow Flag
1 hour & 10 hourFosberg-71 ModelFosberg-71 ModelNelson Model
100 hour & 1000 hourFosberg-71 ModelFosberg-71 ModelNelson Model
Herbaceous and Woody Fuel Moisture ContentHerb fuels classified as dead when dormant.

Transition from dormant/deal fuel moisture to live/full green-up based on climate class in spring 1000 hour based live moisture trend and load transfer
Herb fuels classified as dead when dormant.

Season/Greenness factor based live fuel moisture trend/load transfer unless fuels declared dormant.
Herb fuels classed as dead when dormant.

Green Season/Live Fuel Index based moisture trend and load transfer.


Drought Fuel Load Transfer KBDI used to signal initiation and amount of fuel load transfer.KBDI used to signal initiation and amount of fuel load transfer.
SC, IC, ERC, BIModels unchanged.

Outputs will vary based on differences from new fuel moisture models and new fuel model definitions.
Models unchanged.

Outputs will vary based on differences from new fuel moisture models and new fuel model definitions.
Models unchanged.

Outputs will vary based on differences from new fuel moisture models and new fuel model definitions.
Text (indexed):
  1. NFDRS Fuel Models
  2. Annual vs Perennial Grass
  3. Deciduous vs Evergreen Shrub (88 Version only)
  4. Climate Class Assumptions (78/88 Versions only)
  5. Slope Class Setting

NFDRS Fuel Models

Crosswalk Between 2016 and 78/88 Version Fuel Models

Carrier Fuel CategoryNFDRS 2016 Fuel ModelEquivalent NFDRS 78/88 Fuel Model
GrassVA, L, T
Grass / ShrubWC, D, R, S
BrushXB, F
ForestYG, H, N, P, O, Q, U, E
SlashZI, J, K

78/88/16 NFDRS Fuel Model Definitions (*1988 Version Fuel Model Revisions)

CarrierFuel ModelFuel Model Name1 hour Load t/ac10 hours Load t/ac100 hours Load t/ac1000 hours Load t/acHerb Load t/acWoody Load t/acDrought Load t/ac1 hour SAVHerb SAVWoody SAVBed Depth ftMoist ExtinctHeat Cntnt btu/lb
GRAWestern Annual Grasses0.2------0.3--0.230003000--0.8158000
GRLWestern Perennial Grasses0.25------0.5--0.2520002000--1.0158000
GRV2016 Grass0.1------1.0--020002000--1.0158000
GSC*Pine Grass Savanna0.41.0----0.80.5 (*0.8)1.82000250015000.75208000
GSN*Sawgrass1.51.5------2.02.01600--15003.025 (*40)8700
GSTSagebrush Grass1.00.5----
GSW2016 Grass/Shrub0.50.5----
SHBCalifornia Mixed Chaparral3.54.00.5000011.53.57000012504.5159500
SHOHigh Pocosin2.
SHFIntermediate Brush2.52.01.5----9.02.5700--12504.5159500
SHQAlaskan Black Spruce2.
SHDSouthern Rough2.00.5----0.753.01.51250150015002.0309000
SHX2016 Shrub/Brush4.52.45----1.557.02.52000200015004.4258000
TU/LHShort Needle Pine (Normal Dead)
TU/LGShort Needle Pine (Heavy Dead)
TU/LE*Winter Hardwoods1.5 (*1.0)2.00.25--0.5 (*1.0)0.51.52000200015004.0*258000
TU/LRSummer Hardwoods0.50.50.5--
TU/LUWestern Long Needle Conifer1.51.51.0--
TU/LPSouthern Pine Plantation1.01.00.5--
TU/LY2016 Forest2.52.23.610.16----5.02000----0.6258000
SBKLight Logging Slash2.
SBJIntermediate Logging Slash7.0706.05.5----7.01500----1.3258000
SBIHeavy Logging Slash12.
SBZ2016 Slash4.

NFDRS Grass Fuel Model Descriptions

2016 Fuel Model V

Fuel Model A – This fuel model represents western grasslands vegetated by annual grasses and forbs. Brush or trees may be present but are very sparse, occupying less than one-third of the area. Examples of types where Fuel Model A should be used are cheatgrass and medusa head. Open pinyon-juniper, sagebrush-grass, and desert shrub associations may appropriately be assigned this fuel model if the woody plants meet the density criteria. The quantity and continuity of the ground fuels vary greatly with rainfall from year to year.

Fuel Model L – This fuel model is meant to represent western grasslands vegetated by perennial grasses. The principal species are coarser and the loadings heavier than those in Model A fuels. Otherwise, the situations are very similar; shrubs and trees occupy less than one-third of the area. The quantity of fuels in these areas is more stable from year to year. In sagebrush areas Fuel Model T may be more appropriate.

NFDRS Grass/Shrub Fuel Model Descriptions

2016 Fuel Model W

Fuel Model C – Open pine stands typify Model C fuels. Perennial grasses and forbs are the primary ground fuel, but there is enough needle litter and branch-wood present to contribute significantly to the fuel loading. Some brush and shrubs may be present but are of little consequence. Types covered by Fuel Model C are open, longleaf, slash, ponderosa, Jeffery, and sugar pine stands. Some pinyon-juniper stands may qualify.

Fuel Model D – This fuel model is specifically for the palmetto-gallberry understory-pine association of the southeast coastal plains. It can also be used for the so-called Low Pocosins where Fuel Model O might be too severe. This model should only be used in the Southeast because of the high moisture of extinction associated with it.

Fuel Model N – This fuel model was constructed specifically for the sawgrass prairies of south Florida. It may be useful in other marsh situations where the fuel is coarse and reed like. This model assumes that one-third of the aerial portion of the plants is dead. Fast-spreading, intense fires can occur over standing water.

Fuel Model S – Alaskan and alpine tundra on relatively well-drained sites fit this fuel model. Grass and low shrubs are often present, but the principal fuel is a deep layer of lichens and moss. Fires in these fuels are not fast spreading or intense but are difficult to extinguish.

Fuel Model T – The sagebrush-grass types of the Great Basin and the Intermountain West are characteristic of Fuel Model T. The shrubs burn easily and are not dense enough to shade out grass and other herbaceous plants. The shrubs must occupy at least one-third of the site or the A or L fuel models should be used. Fuel Model T might be used for immature scrub oak and desert shrub associations in the West and the scrub oak-wire grass type of the Southeast.

Timber Understory and Timber Litter Fuel Model Descriptions

2016 Fuel Model Y

Fuel Model H – Used for short-needled conifers (white pines, spruces, larches, and firs). In contrast to FM G fuels, FM H describes a healthy stand with sparse undergrowth and a thin layer of ground fuels. Fires in FM H are typically slow spreading and are dangerous only in scattered areas where the downed woody material is concentrated.

Fuel Model G – Used for dense conifer stands where there is a heavy accumulation of litter and down woody material. They are typically over mature and may be suffering insect, disease, and wind or ice damage – natural events that create a very heavy buildup of dead material on the forest floor. The duff and litter are deep and much of the woody material is more than three inches in diameter. The undergrowth is variable, but shrubs are usually restricted to openings. Types represented here are hemlock-Sitka spruce, coastal Douglas-fir, and wind thrown or bug-killed stands of lodgepole pine and spruce.

Fuel Model E – Used after leaf fall for hardwood and mixed hardwood-conifer types where the hardwoods dominate. The fuel is primarily hardwood leaf litter. It best represents the oak- hickory types and is a good choice for northern hardwoods and mixed forests of the Southeast. In high winds, the fire danger may be underrated because rolling and blowing leaves are not accounted for.

Fuel Model R – This fuel model represents hardwood areas after the canopies leaf out in the spring. It is the growing season version of FM E. It should be used during the summer in all hardwood and mixed conifer-hardwood stands where more than half of the overstory is deciduous.

Fuel Model U – This fuel model represents the closed stands of western long-needled pines. The ground fuels are primarily litter and small branch-wood. Grass and shrubs are precluded by the dense canopy but may occur in the occasional natural opening. Fuel Model U should be used for ponderosa, Jeffery, sugar pine stands of the West and red pine stands of the Lake States. Use FM P for southern pine plantations.

Fuel Model P – Closed, thrifty stands of long- needled southern pines are characteristic. A 2-4 inch layer of lightly compacted needle litter is the primary fuel. Some small diameter branch-wood is present but the density of the canopy precludes more than a scattering of shrubs/grass. FM P has the high moisture of extinction characteristic of the Southeast. The corresponding model for other long-needled pines is FM U.

NFDRS Brush/Shrub Fuel Model Descriptions

2016 Fuel Model X

Fuel Model B – Mature, dense fields of brush six feet or more in height is represented by this fuel model. One-fourth or more of the aerial fuel in such stands is dead. Foliage burns readily. Model B fuels are potentially very dangerous, fostering intense, fast-spreading fires. This model is for California mixed chaparral, generally 30 years or older. The F model is more appropriate for pure chamise stands. The B model may also be used for the New Jersey pine barrens.

Fuel Model O – The O fuel model applies to dense, brush like fuels of the Southeast. In contrast to B fuels, O fuels are almost entirely living except for a deep litter layer. The foliage burns readily except during the active growing season. The plants are typically over six feet tall and are often found under open stands of pine. The high pocosins of the Virginia, North and South Carolina coasts are the ideal of Fuel Model O. If the plants do not meet the six-foot criteria in those areas, Fuel Model D should be used.

Fuel Model F – Fuel Model F represents mature closed chamise stands and oak brush fields of Arizona, Utah, and Colorado. It also applies to young, closed stands and mature, open stands of California mixed chaparral. Open stands of pinyon-juniper are represented; however, fire activity will be overrated at low wind speeds and where ground fuels are sparse.

Fuel Model Q – Upland Alaska black spruce is represented by Fuel Model Q. The stands are dense but have frequent openings filled with usually flammable shrub species. The forest floor is a deep layer of moss and lichens, but there is some needle litter and small diameter branch-wood. The branches are persistent on the trees, and ground fires easily reach into the crowns. This fuel model may be useful for Jack pine stands in the Lake States. Ground fires are typically slow spreading, but a dangerous crowning potential exists. Users should be alert to such events and note those levels of SC and BI when crowning occurs.

NFDRS Slash and Blowdown Fuel Model Descriptions

2016 Fuel Model Z

Fuel Model I – Fuel Model I was designed for clear-cut conifer slash where the total loading of materials less than six inches in diameter exceeds 25 tons/acre. After the slash settles, and the fines (needles and twigs) fall from the branches, Fuel Model I will overrate the fire potential. For lighter loadings of clear-cut conifer slash use Fuel Model J, and for light thinnings and partial cuts where the slash is scattered under a residual overstory, use Fuel Model K.

Fuel Model J – This model complements Fuel Model I. It is for clear-cuts and heavily thinned conifer stands where the total loading of material less than six inches in diameter is less than 25 tons per acre. Again as the slash ages, the fire potential will be overrated.

Model K – Slash fuels from light thinnings and partial cuts in conifer stands are represented by Fuel Model K. Typically the slash is scattered about under an open overstory. This model applies to hardwood slash and to southern pine clear-cuts where loading of all fuels is less than 15 tons/acre.

Annual vs Perennial Grass

The loading of fine fuels associated with annual grasses shifts from live to dead and stays there for the duration of the season. For perennial grasses, the shift from live to dead is much slower and may even stop or reverse if the right combinations of temperature and precipitation occur during the season.

Deciduous vs Evergreen Shrub (88 Version only)

In the 1988 revision to the NFDRS, separate equations were developed for deciduous and evergreen shrub vegetation, requiring users to enter a code indicating whether their local shrub vegetation is deciduous (D) or evergreen (E).

Climate Class Assumptions (78/88 Versions only)

Climate ClassNameEcologyDescriptionDormant FM Minimums
100 hours
Dormant FM Minimums
1000 hours
Dormant FM Minimums Woody78 Transition Rates, in days
78 Transition Rates, in days Curing
1Arid and Semi-AirdDesertSonoran, Mohave, Short grass prairie, interior west scrub lands10%15%50%7 daysControlled by 1000 hour fuel moisture between full green-up and dormancy
2Sub-humidSteppe and SavannaAK interior, chaparral, oak and pine woodlands15%20%60%14 days
Controlled by 1000 hour fuel moisture between full green-up and dormancy
3Sub-humid and humidSavanna and ForestBluestem prairie, grass-oak hickory savanna, Eastern US, western forests20%25%70%21 daysControlled by 1000 hour fuel moisture between full green-up and dormancy
4WetRain forestCoastal forests25%30%80%28 daysControlled by 1000 hour fuel moisture between full green-up and dormancy

Slope Class Setting

Slope ClassSlope RangeEffective MidpointSlope Coefficient
Text (indexed):
  1. Observations and Forecasts
  2. Primary System Components & Indices
  3. Wildland Fire Assessment System (WFAS)
  4. Weather Information Management System (WIMS)
  5. Pocket Cards

Observations and Forecasts

Fire Weather Observations are collected and maintained according to standards established in the Interagency Wildland Fire Weather Station Standards and Guidelines, PMS 426-3.

Lightning Activity Level (LAL)

LAL 1No Thunderstorms.
LAL 2Isolated thunderstorms. Light rain will occasionally reach the ground. Lightning is very infrequent, 1-5 cloud-to-ground strikes in a five minute period.

Widely scattered thunderstorms. Light to moderate rain will reach the ground. Lightning is infrequent, 6-10 cloud-to-ground strikes in a five minute period.

LAL 4Scattered thunderstorms. Moderate rain is commonly produced. Lightning is frequent, 11-15 cloud-to-ground strikes in a five minute period.
LAL 5Numerous thunderstorms. Rainfall is moderate to heavy. Lightning is frequent and intense, greater than 15 cloud-to-ground strikes in a five minute period.
LAL 6Same as LAL 3 except thunderstorms are dry (no rain reaches the ground). This type of lightning has the potential for extreme fire activity and is normally highlighted in fire weather forecasts with a Red Flag Warning.

Primary System Components and Indices

Ignition Component (IC)

The Ignition Component is a rating of the probability that a firebrand will cause a fire requiring suppression action. Expressed as a probability; it ranges on a scale of zero to 100. An IC of 100 means that every firebrand will cause an actionable fire if it contacts a receptive fuel. Likewise, an IC of zero would mean that no firebrand would cause an actionable fire under those conditions. Note the emphasis is on action.

Spread Component (SC)

The Spread Component is a rating of the forward rate of spread of a headfire. Deeming, et al (1977), states that, “the Spread Component is numerically equal to the theoretical ideal rate of spread expressed in feet-per-minute. Highly variable from day to day, the Spread Component is expressed on an open-ended scale; thus it has no upper limit."

Energy Release Component (ERC)

The Energy Release Component is a number related to the available energy, BTU per unit area square foot, within the flaming front at the head of a fire. Daily variations in ERC are due to changes in moisture content of the various fuels present, both live and dead. Since this number represents the potential heat release per unit area in the flaming zone, it can provide guidance to several important fire activities. It may also be considered a composite fuel moisture value as it reflects the contribution that all live and dead fuels offer to potential fire intensity. It should also be pointed out that the ERC is a cumulative or build-up type of index. As live fuels cure and dead fuels dry, the ERC values get higher thus providing a good reflection of drought conditions. The scale is open-ended or unlimited and, as with other NFDRS components, is relative. Conditions producing an ERC value of 24 represent a potential heat release twice that of conditions resulting in an ERC value of 12.

As a reflection of its composite fuel moisture nature, the ERC becomes a relatively stable evaluation tool for planning decisions that might need to be made 24 to 72 hours ahead of an expected fire decision or action. Since wind does not influence the ERC calculation, the daily variation will be relatively small. The 1000 hour time lag fuel moisture (TLFM) is a primary entry into the ERC calculation through its effect on both living and dead fuel moisture inputs. There may be a tendency to use the 1000 hour TLFM as a separate index for drought considerations. A word of caution – any use of the 1000-hour TLFM as a separate index must be preceded by an analysis of historical fire weather data to identify critical levels of 1000 hour TLFM. A better tool for measurement of drought conditions is the ERC since it considers both dead and live fuel moistures.

Burning Index (BI)

The Burning Index is a number related to the contribution of fire behavior to the effort of containing a fire. The BI is derived from a combination of Spread and Energy Release Components. It is expressed as a numeric value closely related to the flame length in feet multiplied by ten. The scale is open ended which allows the range of numbers to adequately define fire problems, even in time of low to moderate fire danger. It’s important to remember that computed BI values represent the near upper limit to be expected on the rating area. In other words, if a fire occurs in the worst fuel, weather, and topography conditions of the rating area, then these numbers indicate its expected fireline intensities and flame length. Studies have indicated that difficulty of containment is not directly proportional to flame length alone but rather to fireline intensity; the rate of heat release per unit length of fireline (Byram 1959). The use of fireline intensity as a measure of difficulty shows that the containment job increases more than twice as fast as BI values increase. It is still safe to say that flame length is related to fireline intensity because BI is based on flame length.

Lightning Occurrence Index (LOI)

The Lightning Occurrence Index is a numerical rating of the potential occurrence of lightning-caused fires. It is intended to reflect the number of lightning caused fires one could expect on any given day. The Lightning Occurrence is scaled such that a LOI value of 100 represents a potential of 10 fires per million acres. It is derived from a combination of Lightning Activity Level (LAL) and Ignition Component. To effectively develop this index the user must perform an extensive analysis to develop a local relationship between thunderstorm activity level and number of actual fire starts that result. Since our ability to accurately quantify thunderstorm intensity is limited it is difficult to develop a relationship between activity and fire starts. Thus the Lightning Occurrence Index is seldom used in fire management decisions. Local fire managers should monitor the lightning activity level provided by the National Weather Service, and with a little experience can develop their own rating of lightning fire potential.

Human Caused Fire Occurrence Index (MCOI)

This is a numeric rating of the potential occurrence of human-caused fires. Similar to the Lightning Occurrence Index, this value is intended to reflect the number of human-caused fires one could expect on any given day. It is derived from a measure of daily human activity and its associated fire start potential, the human caused fire risk input, and the ignition component. The MCOI is scaled such that the number is equal to ten times the number of fires expected that day per million acres. An index value of 20 represents a potential of teo human caused fires per million acres that day if the fuel bed was receptive for ignition. The original developers of the National Fire Danger Rating System recognized that where the total fires per million acres average twenty or fewer, the evaluations are questionable. This has been validated through application. As with the Lightning Occurrence Index, the Human-caused Fire Occurrence Index requires considerable analysis to establish a local relationship between the level of human activity and fire starts. Since human activity is fairly constant throughout the season and human-caused fire occurrence in, for example, the Pacific Northwest, is relatively low in terms of fires per million acres per day, most analyses result in very low risk inputs that don’t change much from day to day. Few fire managers, if any, are using this index in making day-to-day decisions.

Fire Load Index (FLI)

Fire Load Index is a rating of the maximum effort required to contain all probable fires occurring within a rating area during the rating period. The FLI was designed to be the end product of the NFDRS – the basic preparedness or strength-of-force pre-suppression index for an administrative unit. It was to be used to set the readiness level for the unit. It focuses attention upon the total fire containment problem. Because the FLI is a composite of the various components and indexes of the NFDRS, including the local lightning and human caused fire risk inputs, the comparability of values varied significantly from one unit to another. To be useful managers must establish the relationship between the FLI calculated for their unit and the true fire containment effort needed. The FLI is represented as a number on a scale of 1-100. It provides no specific information as to the nature of the potential fire problem as individual indexes and components do. Because the Fire Load Index is a composite of several pieces of the NFDRS, its utility is impacted by of the inherent weaknesses of the individual components and indexes. Very few fire management decisions are made based on the Fire Load Index alone.

Keetch-Byram Drought Index (KBDI)

This index is not an output of the National Fire Danger Rating System itself but is often displayed by the processors used to calculate NFDRS outputs. KBDI is a stand-alone index that can be used to measure the effects of seasonal drought on fire potential. The actual numeric value of the index is an estimate of the amount of precipitation (in 100ths of inches) needed to bring the soil back to saturation (a value of zero is complete saturation of the soil). Since the index only deals with the top eight inches of the soil profile, the maximum KBDI value of 800 or 8.00 inches of precipitation would be needed to bring the soil back to saturation. The Keetch-Byram Drought Index’s relationship to fire danger is that as the index value increases, the vegetation is subjected to increased stress due to moisture deficiency. At higher values desiccation occurs and live plant material is added to the dead fuel loading on the site. Also an increasing portion of the duff/litter layer becomes available fuel at higher index values. If you are using the 1978 fuel models, KBDI values can be used in conjunction with the National Fire Danger Rating System outputs to aid decision making. If you are using the modified NFDRS fuel models that were developed in 1988, KBDI values are a required input to calculate daily NFDRS outputs. Since most fire danger stations are not being operated when the soil is in a saturated condition, it is necessary to estimate what the KBDI value is when daily observations are began. The technical documentation describing the KBDI includes methodology to estimate the initiating value and is included in the attached reference list. Most processors include a default initiation value of 100.

Wildland Fire Assessment System (WFAS)

WFAS provides public access to standard Fire Potential/Danger depictions, Fire Weather information, Fuel Moisture/Drought products, and assorted Experimental Products produced by the Rocky Mountain Research Station’s Fire, Fuel and Smoke Science Program.

Operating with fire weather observations from WIMS (4.3.4), gridded forecasts from NWS National Digital Forecast Database (NDFD), and gridded fire danger climatology dating to 1979.

Weather Information Management System (WIMS)

NAP Access Portal requires login and provides authorized access for management of RAWS station catalogs, observations, NFDRS calculations, and source data for other portals such as the Enterprise Geospatial Portal (EGP) and Wildland Fire Assessment System (WFAS).

WIMS Users Guide

Pocket Cards

FAM-IT Portal provides access to background, instructions, standards, and approved cards throughout the US.

Example of NWCG standard Fire Danger Pocket Card.

The Fire Danger Pocket Card provides a format for interpreting and communicating key index values provided by the National Fire Danger Rating System. The objective is to lead to greater awareness of fire danger and subsequently increased firefighter safety. The Pocket Card provides a description of seasonal changes in fire danger in a local area. It is useful to both local and out-of-area firefighters.

The Pocket Card has very important day-to-day pre-suppression uses. When the morning and afternoon weather is read each day, the actual and predicted indices are announced. Firefighters can reference their card and assess where today falls in the range of historical values for danger-rating. This important information should be discussed at morning crew meetings, tailgate safety meetings, incident briefings, etc.

Local fire management personnel can produce the cards using Fire Family Plus. Cards should be developed locally with local fire management involvement to meet local fire management needs.

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Interagency Predictive Services

During the active fire season, the National Interagency Coordination Center (NICC) and each geographic area predictive service office is staffed seven days a week to support the assessment needs of fire program managers, incident personnel, and groups coordinating regional fire management resources.

Map of US Geographic Areas. Each Geographic Area includes a predictive services unit that assesses area conditions and produces outlook products.

All the geographic area predictive service products can be referenced from the National Interagency Coordination Center (NICC) outlooks page.

A National 7-Day Significant Fire Potential Outlook is produced each day.

Example 7-day Significant Fire Potential Outlook product. These are produced daily and provide an outlook for the next 7 days.

This 7-day outlook also includes forecasts for the weather elements, fuel moistures, and fire danger indices that are used to produce these potential classifications. These 7-day forecasts represent averages for areas defined by the geographic area to be climatologically distinct.

Other standard products include daily, monthly, and seasonal assessments. Several produce multi-media briefings that can be linked from the outlooks page.