Coos Forest Protective AssociatioN
National Fire Danger Rating System - (NFDRS)
Coos FPA Pocket Card Image
Overview of NFDRS
The NFDRS relates to the potential of a fire that is just starting. It does not factor in spotting, crowning, or erratic
fire behavior. The NFDRS is often referred to as "Indices".
Fire danger is rated from a worst case approach for the fuel model chosen for a given station. We are using existing BLM, USFS, and ODF Remote Automatic Weather Stations (RAWS). Salem derives this information from Weather Information Management System (WIMS). Fire weather is measured by the station at the time of day when fire danger is normally highest. The stations are purposely sited in the open, at midslope, on southerly or westerly exposures. Fuel models used are natural forest fuels, not activity fuels (slash). We can expect fires in slash fuels to burn far "hotter" and faster then predicted by NFDRS.
Explanation of the Indices
Spread Component (SC)
The SC integrates the effect of wind and the moisture content of live and dead fuels to give an indication of rate of spread. This indice will vary significantly from day to day to reflect the effect of wind and fuel moisture content. Fuel moisture content is influenced largely by precipitation but is also influenced by relative humidity which includes east winds, marine air, and fog.
Energy Release Component (ERC)
The ERC is used as an indicator of effects of more long term drying and curing of the forest fuels. The indice will respond slower to day to day temperatures and humidity. This is most useful in evaluating and adjusting Industrial Fire Precautionary Levels and Public Use Restrictions.
Burning Index (BI)
The BI is derived from the combination of the SC and the ERC. This will fluctuate somewhat day to day to reflect local weather, a significant weather change would be needed to cause a significant change in the BI. This indice is used for evaluating the Daily Fire Danger and staffing needs to correspond with the daily fire danger.
Ignition Component (IC)
The IC is an indicator to the probability of a firebrand producing a fire that will require suppression action. This indice is influenced by the relative humidity and the temperature of the fuel. The IC is useful in that it helps in areas such as assessing the potential of a fire spotting.
Links For NFDRS Information
Gaining an Understanding of the NFDRS
NFDRS Weather Station Standards
NFDRS Basic Equations
NFRDS Historic Collection