National fire weather outlooks issued by the Storm Prediction Center

The Storm Prediction Center (SPC) works in partnership with National Weather Service (NWS) forecast offices in providing fire weather guidance to various federal and emergency management concerns. The SPC is in its second year of issuing national fire weather outlooks. These outlooks parallel the traditional SPC Day 1 and Day 2 general and severe thunderstorm outlooks. The fire weather outlooks are issued once per day at 4 AM (CST/CDT) year round. The Day 1 outlook is valid from 12 to 12 UTC and the Day 2 outlook covers the following 24-hour period. All SPC fire weather graphic and text products are available to anyone via the Internet at: www.spc.noaa.gov/fire.

In producing national fire weather guidance, SPC meteorologists evaluate short and long-term precipitation patterns, as well as traditional drought and fire indices (i.e. live and dead fuel moisture and fire danger rating categories). Once an area has been identified as favorable for wildfires due to pre-existing conditions, meteorological parameters critical to fire behavior are assessed. These parameters include forecasts of surface temperature, humidity, and wind speed, as well as changes in thermodynamic and wind profiles. Conditions favoring high-based (dry) thunderstorms, critical wind shifts, and frontal passages are also evaluated.

If meteorological conditions for either Day 1 or Day 2 are favorable for the start or spread of wildfires, then those areas are highlighted on a U.S. map and are accompanied by a technical forecast discussion. Since the SPC covers the lower 48 states, small-scale features and local effects are not covered. It is hoped that SPC forecasters capture the large-scale fire weather conditions, with the local NWS forecast offices specializing in forecasting small-scale weather conditions critical to fire behavior in their areas of responsibility.

Beginning in May 1999, the SPC began using numerical risk categories for large-scale areas of concern. In addition, new model-based products geared specifically towards forecasting dry thunderstorms were added to the web page. Examples of SPC guidance and results will be shown at the conference.