Verification Analysis of Red Flag Warnings in the Reno, Nevada County Warning Area

Red Flag Warnings (RFWs) are a product issued by the National Weather Service (NWS) to indicate when conditions are conducive to fire development and spread. This product alerts firefighters, emergency managers, and other government officials to a potential increase in fire activity so they can effectively place resources to mitigate the potential threat. Red Flag Warnings are issued based on set criteria involving a combination of relative humidity and wind speed for a given region. If a warning is issued and the criteria is not met, it is considered “unverified” and if criteria is met but a warning is not issued, it is considered “missed”. The purpose of verification analysis is to determine what improvements can be made to the forecasting and communication process of RFWs.

The primary challenge in predicting fire weather in the Reno area is the drastic change in elevation across the Sierra range and Great Basin. This is further amplified by the NWS Fire Weather Zones which each encompass a large area of the NWS Reno County Warning Area (CWA). Other challenges that can play a varying role are forecasting model disagreement and the threat of over-warn which can create an apathetic environment that overshadows more severe fire weather events. This research explores missed and unverified RFW events from 2011 to 2017 to determine what improvements can be made to increase the accuracy and efficiency of predicting RFW events in the NWS Reno CWA.