An evaluation of the updated National Fire Danger Rating System

The National Fire Danger Rating System (NFDRS) uses weather, fuels, and fire occurrence data to estimate today’s or tomorrow’s fire danger for a given area. In the United States, the National Fire Danger Rating System has been used to support operational fire decision making for the last 50 years. In that timeframe it has been updated only three times. Spurred by Rocky Mountain Research Station fire danger rating system developers in 2014, the latest update, Version 4, went into service in 2018 and was released for nationwide, operational use in 2023. 

Version 4 of the National Fire Danger Rating System implements new live and dead fuel moisture models. It also uses a simpler set of five existing surface fuel models. Because the National Fire Danger Rating System is designed to be modular, these updates do not interrupt the overall structure of the system. Version 4 is simpler and more automated than previous versions, while still meeting the needs of decision-makers and fire managers.

Rocky Mountain Research Station scientists recently published an evaluation of the updated National Fire Danger Rating System. They found that Version 4 is as good or better than older versions at predicting fire days, large fire ignition days, and various measures of fire seasonality – despite the more streamlined process. They also found that modeled and measured live fuel moisture content values were highly correlated. Further, the simplified set of surface fuel models used in Version 4 effectively eliminates cross-correlation between fuel models and reduces complexity in training and operational use. 

Through the iterative process of research, development, implementation, and evaluation, researchers have established a working framework and recommendations for future revisions to the National Fire Danger Rating System. This next-generation fire danger model paves the way for a nationally-relevant, fully-automated fire danger rating system that can adequately depict fire danger across a range of climates and fuel types but that is simpler to understand and communicate, and could be adapted for use worldwide.  

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