3. Types of Fire Weather Forecasts

There are three primary types of fire weather forecasts: 1) the Fire Weather Planning (Zone) Forecast, 2) the spot weather forecast, and 3) the Incident Weather Forecast. In addition to these three forecast types, the National Weather Service (NWS) Point Forecasts will also be discussed in the context of their application to wildland fire.

The Fire Weather Planning (Zone) Forecast

Purpose

The fire weather planning (zone) forecast is primarily used for input in decision-making related to pre-suppression and other planning. Because this forecast type covers a relatively large geographic area, it is only to be used for planning and situational awareness. Examples of planning may include setting preparedness levels or day-to-day staffing needs.

Where it is Produced

The fire weather planning (zone) forecast (herein referred to as the zone forecast), is produced from the NWS Weather Forecast Office (WFO) that covers forecasts for the area where the zone forecast is produced. You may also see the zone forecast referred to as the Zone Forecast Product (ZFP) in NWS forecasts.

Geographic Area Covered

A fire weather zone is generally a small, county-sized area of land with similar climate, weather, and terrain characteristics. For example, the fire weather zones for the Rapid City NWS WFO (western South Dakota and northeastern Wyoming ) can be found in Figure 1 (it should be noted that fire weather zones in Alaska tend to be much larger than those within the Contiguous US). The weather variables presented in the forecast represent average conditions across the zone. Because zones are built to represent climatologically similar areas (that often follow topography), smaller zones are typically found in areas of complex terrain while large zones may be found across prairies or areas of more homogenous terrain.

Map of fire weather zones for western South Dakota and eastern Wyoming..

Figure 1: Fire Weather Zones for western South Dakota and eastern Wyoming.

The Fire Weather Planning (Zone) Forecast should primarily be used in decision-making related to pre-suppression and other planning purposes.

How to Use a Zone Forecast

The zone forecast should be read at the start of your shift. This is your opportunity to see what type of weather can be expected for the operational period and if there are any specific concerns that may negatively impact you on an emerging incident. The Headlines and Discussion sections may be the most important part of the forecast as they will bring to your attention any potential problems of the day. Also, look at the trend of the forecast as compared to previous days. What makes today different than yesterday and what may make it different than tomorrow?

Often, a zone forecast may be the only weather forecast you have when first arriving on an incident as an initial attack resource. This requires you to base your weather-related decisions on the forecast and from what you learned in the weather portions of the S-190/S-290 series of fire behavior courses.

Once on an incident, examine your forecast, and your surroundings then note important terrain features. This will help you build a mental model of the forecast for the day. This process is further described in Building a Mental Model of the Weather Forecast. Furthermore, you should start taking your own weather observations as soon as feasible so that you can compare your observed weather to the forecast. Taking observations will also help you in completing a request for a spot weather forecast.

NWS Criteria and Typical Product Format

The specific guidelines for when a zone forecast is produced, the description of the zone, and the specific weather variables to be included in the forecast are governed by the local Fire Weather Annual Operating Plan (FWAOP). The FWAOP is produced in collaboration with the regional WFOs and land management agencies, often through the respective Geographic Area Coordination Center (GACC).

Product format varies for each of the NWS WFOs. Although the product will contain most, if not all, of the variables described in the previous section of this document, there may be notable differences in layout and presentation. Familiarize yourself with the layout of your local zone forecast and if you have question, ask a meteorologist from your local NWS WFO.

Communication Mechanism

The zone forecasts are a written forecast produced and disseminated by the NWS through their web portal. Additionally, the forecasts are often reported by your local dispatch office via the radio network.  

Expectation of Service

Out of three fire weather forecast types presented in this document, the zone forecast is the most stand-alone product. It is produced at a WFO without any input from wildland fire managers. This routine product, generated through a highly automated process, should be produced at least once daily during the local fire season. If you have questions regarding the forecast, you can still contact your local WFO but do not expect the forecasters to specifically tailor the product to your needs as it covers a large geographic area.

The Spot Weather Forecast

Purpose

The Spot Weather Forecast supports wildfire and prescribed fire operations, natural resource management, marine incidents, search, and rescue operations, hazardous materials incidents, and other threats to public safety. In nearly all cases, the spot forecast support incidents managed by a federal, tribal, state, or local government agency. Spot forecasts are non-routine, near-term forecasts providing actionable information for incident management.

Where it is Produced

The spot forecast, like the zone forecast, is produced by your local NWS WFO. The spot forecast is first created through an automated process at the local WFO. It is then edited by a meteorologist using the information provided in the spot request form, from local experience, and by analyzing local terrain influences.

Geographic Area Covered

The spot forecast is aptly named as it is a forecast for a spot or a small area. The size of the area that the spot forecast is valid for is dictated by the incident for which the request was made. A request could be made for a small prescribed fire of less than ten acres or for an emerging wildfire of several thousand acres.

Spot Weather Forecasts are issued to support wildfire and natural resource management, as well as other threats to public safety.

How to Use a Spot Forecast

A spot forecast must be requested by a governmental agency through the spot weather request form. Your local dispatch center can also assist you with the request if internet services are not available. When requesting a spot weather forecast, be sure to include site-specific information on the request form.

Spot weather forecasts generally take 30 to 60 minutes to complete once the request is received by the local NWS WFO. If a spot forecast is requested for a prescribed fire, it can be submitted up to one day in advance of the ignition time. If a weather forecast is necessary more than one day ahead of time, it is suggested that a zone or point forecast be used. As you go through your operational period, be sure to continuously observe the weather and note any changes from the weather forecast. More information on this process can be found in Building a Mental Model of the Weather Forecast that describes building a mental model of the weather forecast.

Submit a request for a spot forecast at the start of each operational period if working on a wildfire or a prescribed burn. The accuracy of forecasts diminish with time so it is imperative that you have the most up-to-date forecast possible.

NWS Criteria and Typical Product Format

The NWS requires that the spot weather forecast contains these variables: header including forecast time/date valid, headlines, and discussion; sky/weather; temperature; relative humidity; and wind. Other forecast variables may be requested on the spot request form or may be included automatically per the local FWAOP. Spot forecasts generally contain three to four forecast periods and an extended forecast may be included if requested.

The NWS has standardized the format of the spot weather forecast to ensure continuity across the country. This format contains the same elements discussed in the previous section.

Communication Mechanism

Spot weather forecasts are requested and disseminated via the aforementioned spot weather request page. These products are written forecasts that can be included within Incident Action Plans or Prescribed Burn Plans. If internet is unavailable, they can be requested and/or received via radio from your local dispatch center.

Expectation of Service

You should have a much higher expectation of service with the spot weather forecast than you will have with a zone weather forecast. It is expected that the NWS forecasters know the terrain you are working in, remotely monitor the ongoing weather conditions relative to the spot forecast, and provide updates, and/or corrections to the user when necessary. If critical fire weather conditions are impending, the forecaster will provide a written update to the forecast and verbally confirm with the end user that the critical update was received. However, it is up to you to monitor the weather and inform the forecaster if conditions are deviating too far from the forecast.

To ensure you receive the best service possible, it is imperative that the wildfire manager also communicate any important weather observations or comments back to the local WFO. Oftentimes weather observations made by incident personnel are the only observations available in the vicinity of the incident and these should be communicated to the WFO.

There is a feedback section within the spot request form, and it is expected that you provide feedback, good or bad, on the quality of the forecast back to the NWS. An example of feedback could include the relative accuracy of the forecast to the observations made at the incident. If the spot forecast calls for a westerly wind but persistent northerly winds are being observed, you need to communicate these observations back to the WFO. They may then be able to create an updated forecast that is more accurate because of the observations you provided.

The Incident Weather Forecast

Purpose

The purpose of the incident weather forecast is to provide information to support the incident objectives. Operations may use the forecast to develop strategic plans to meet the incident objectives. Other units may use the forecast as well: for example, the logistics section may need to know if strong winds are likely to move through the Incident Command Post (ICP). Therefore, the written forecast needs to be broad enough to encompass the needs of the entire incident, yet specific enough to provide information that is actionable.

Where it is Produced

The incident weather forecast is produced on site by a qualified Incident Meteorologist (IMET), generally located at the ICP. Most Type I and Type II incidents will have an IMET embedded within the planning section of the Incident Management Team (IMT). Occasionally, an IMET will also be dispatched to Type III incident or other smaller events. The incident weather forecast can be found within the Incident Action Plan (IAP) or similar incident document.

Geographic Area Covered

As with a spot weather forecast, the incident forecast is made for the area of the incident for which it is produced. With a wildfire, this might be several hundred to tens of thousands of acres. Like the zone and spot forecasts, the IAP forecast may not be accurate for each area of the fire due to a large potential size.

Incident Weather Forecasts are produced by on-scene Incident Meteorologists to support the incident objectives.

How to Use an Incident Weather Forecast

Incident weather forecasts are typically produced twice a day; one forecast for each 12-hour day and night operational period. The incident weather forecast should be used in the same manner as the spot weather forecast. The benefit of this type of forecast is that an IMET will generally be on site and available to brief incident personnel. Fire weather briefings should cover the main elements of the forecast but are also used to highlight specific weather hazards or information regarding uncertainties within the forecast.

NWS Criteria and Typical Product Format

The incident weather forecast will include the same mandatory elements as contained within the spot weather forecast: a header including forecast time/date valid, headlines, and discussion; sky/weather; temperature; relative humidity; and wind. Other forecast variables may be included at the discretion of the IMET, the Planning Section Chief (PSC), or Incident Commander (IC). The format for the forecast will resemble that of the spot weather forecast but may be adjusted depending on the needs of the IMT and structure of the IAP.

Communication Mechanism

The incident forecast is a written product disseminated through the IAP. The benefit of having an IMET on scene, however, is the ability to directly communicate with the meteorologist if the written forecast does not sufficiently meet the needs of the incident. On large incidents, the weather may vary from branch to branch, or even from division to division. The IMET can communicate these differences through operational briefings and direct communication to affected parties. Furthermore, when a high-impact operation such as a large burnout is being planned, the IMET can create an incident spot weather forecast addressing the specific needs of that operation. If an incident spot forecast is desired, it should be communicated up through the chain of command so that the IMET is notified and can promptly produce the forecast.

The IMET will keep an overwatch on conditions affecting the fire. If the weather conditions deviate from the incident forecast, an updated forecast can be made. This forecast update will then most likely be disseminated via incident radio channels.

Observations should always be made on the fireline and it is very important that a copy of these observations be made available to the IMET at least once per day. Large incidents may be in areas of complex terrain which affects the local weather. Knowing how the weather conditions evolve each day around the incident will help the IMET improve forecast accuracy in following days.

Expectation of Service

The incident weather forecast has the highest level of service as compared to the other fire weather forecast types. This is because the IMET is on scene and able to communicate in person or via the radio to fire personnel. Two-way communication is key when working with an IMET. It is the IMETs responsibility to produce accurate products, but it is also the duty of fireline personnel to ensure that observations are being made, recorded, and delivered to the IMET in a timely fashion. Additionally, it is up to the firefighters to communicate any potential discrepancies between the forecast and the observed conditions back to the IMET.

Other Relevant Forecast Products

Point Weather Forecast

Purpose

The point weather forecast is derived from the NWS National Digital Forecast Database (NDFD), a seamless mosaic of digital forecasts for the United States. The purpose of the NDFD is to make NWS digital data accessible to all public and private entities, including the wildfire community. The point weather forecast is not a fire weather forecast per se, but it can be used for situational awareness as it includes all fire weather elements.

Where it is Produced

The data that are incorporated into the NDFD (and therefore the point forecasts) are produced by the local NWS WFOs and the National Centers for Environmental Prediction (NCEP). These data are then combined to form a nationwide suite of gridded forecasts of sensible weather elements. The information included within a planning fire weather (zone) forecast is often directly taken from the NDFD grids then averaged across the larger geographic fire weather zone.

Geographic Area Covered

The point forecasts are extracted from a 2.5-km grid across the Contiguous US, Guam, and Hawaii; a 3-km grid across Alaska; and a 1.25-km grid over Puerto Rico. These grids represent areas that are much smaller in geographic extent than area contained within a fire weather zone for a fire weather planning forecast.

How to Use a Point Weather Forecast

Because point weather forecasts give the weather forecast by the hour, they are a convenient way to help you visualize how the weather will change through the period. They can be most helpful in identifying times when the inversion will break, when cloud cover will move through, or when an expected wind shift may occur. Point forecasts can be especially helpful when building your mental model of the weather forecast, as described in Building a Mental Model of the Weather Forecast.

Point forecasts are made for a 7-day period and are updated at least once per day. They are especially useful for situational awareness when you need to know what the weather might be doing several days in advance.

NWS Criteria and Typical Product Format

The criteria for what is included in the NDFD is expansive and covers practically all potential forecast variables. Because point forecasts rely on NDFD data, there is not a standard forecast format. All forward-facing NWS products rely on some aspect of the NDFD, including the fire weather forecasts. Point forecasts from the NDFD products are hourly forecasts that can be displayed in either tabular or graphical format, depending on the needs of the end user. An example of a point weather forecast is given in Figure 2. Note that fire weather forecast elements can be selected as the data are extracted from the larger NDFD that contains those variables.

Communication Mechanism

Point forecasts can be found on the NWS homepage or via the NDFD homepage. Forecast data are also transmitted via the NWS Weather Radio network.

Expectation of Service

The expectation of service is similar to that of the planning fire weather (zone) forecast. These products are automatically generated by local NWS offices, not necessarily reviewed by a human forecaster, and are not specifically intended for use by wildfire managers. All good reasons to request a spot weather forecast, if your needs dictate a quality forecast.

Area Forecast Discussion

The Area Forecast Discussion (AFD) is a product issued by forecasters at each NWS WFO. The purpose of the AFD is to describe the scientific reasoning used to create the 7-day forecast product. The AFD represents the meteorologist’s thought process while creating the forecast and may give additional beneficial insight into the forecast itself, forecaster’s confidence, and provide additional context for any watches, warnings, or advisories that may be in effect.

An optional section of the AFD, when used, describes the current, and expected fire weather conditions. This section of the discussion focuses on the first 48 hours of the fire weather forecast and will emphasize Fire Weather Watches and or Red Flag Warnings.

The AFD simply provides more context for the forecast issued by the WFO. The AFD, sometimes called the Forecaster’s Discussion, can be found via a link on the NWS WFO homepage.

National Weather Service graphical point forecast.

Figure 2: NWS graphical point forecast.

 

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Page Last Modified / Reviewed: 
2021-04-28