Fire Weather

 Fire Weather

• Fire weather is the use of meteorological parameters such as relative humidity, wind speed and direction, mixing heights, and soil moisture to determine whether conditions are favorable for fire growth and smoke dispersion.

• Red Flag Warning is a term used by fire-weather forecasters to call attention to limited weather conditions of particular importance that may result in extreme burning conditions. It is issued when it is an on-going event, or the fire weather forecaster has a high degree of confidence that Red Flag criteria will occur within 24 hours of issuance. Criteria includes:

  • a sustained wind average 15 mph or greater

  • relative humidity less than or equal to 25 percent and

  • a temperature of greater than 75 degrees F.

  • In some states, dry lightning and unstable air are criteria. A Fire Weather Watch may be issued prior to the Red Flag Warning.

• Lightning Activity Level (LAL) is an objective rating system used in the NFDRS that indicates the amount of cloud-to-ground lightning observed or forecast in a given area.

• Haines Index is a lower atmospheric stability and dryness index that can be one predictor of large fire growth.

• For the daily fire weather forecast see: weather.gov/wrh/fire?wfo=mso