Fire Danger Background

  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.
Page Last Modified / Reviewed: 
2019-04-09