Red Flag Warning
As the temperatures in Southern Arizona heat up, and the moisture in the air decreases, we start getting a lot of Red Flag Warnings for the various parts of the state. I’ve known intuitively what these warnings are about, especially since I was a wildland firefighter for a season, but wanted to find out some more details.
Red Flag Warnings are issues by the National Weather Service to inform firefighting authorities and land management offices that the conditions are right for wildland fire ignition and propagation. For these offices, the issuance of a Red Flag Warning helps them prepare for the potential fires brought on by drought, low humidity and high winds with potential lightning. For the general public, a Red Flag Warning means there is a high fire danger with increased probability of a quickly spreading vegetation fire in the area in the next 24 hours.
The weather criteria for fire weather watches and red flag warnings varies with each Weather Service Office’s warning area based on the local vegetation type, topography, and distance from major water sources but usually includes the daily vegetation moisture content calculations, expected afternoon high temperature, afternoon minimum relative humidity and daytime wind speed.
Related to, but of less severity than, a Red Flag Warning is a Fire Weather Watch. which alerts the public and fire fighting agencies that conditions may exist for a Red Flag Warning after the initial forecast period (12 hours). It is generally issued 12 to 48 hours in advance of the conditions, but can also be issued up to 72 hours in advance. That watch then remains in effect until it expires, is canceled, or upgraded to a Red Flag Warning.
Here’s an example of a Red Flag Warning for Flagstaff, AZ.
WWUS85 KFGZ 120342 RFWFGZ RED FLAG WARNING NATIONAL WEATHER SERVICE FLAGSTAFF AZ 842 PM MST WED JUN 11 2008 AZZ111>117-140-120445- /O.EXP.KFGZ.FW.W.0023.000000T0000Z-080612T0400Z/ CHUSKA MOUNTAINS AND DEFIANCE PLATEAU (FIRE WEATHER ZONE 111)- LITTLE COLORADO RIVER VALLEY IN COCONINO COUNTY (FIRE WEATHER ZONE 112)- LITTLE COLORADO RIVER VALLEY IN NAVAJO COUNTY (FIRE WEATHER ZONE 113)- LITTLE COLORADO RIVER VALLEY IN APACHE COUNTY (FIRE WEATHER ZONE 114)-WESTERN MOGOLLON RIM (FIRE WEATHER ZONE 115)- EASTERN MOGOLLON RIM (FIRE WEATHER ZONE 116)- WHITE MOUNTAINS (FIRE WEATHER ZONE 117)- NORTHEAST PLATEAUS AND MESAS SOUTH OF HWY 264 (FIRE WEATHER ZONE 140)- 842 PM MST WED JUN 11 2008 ...RED FLAG WARNING WILL EXPIRE AT 9 PM MST THIS EVENING... THE RED FLAG WARNING WILL EXPIRE AT 9 PM MST THIS EVENING. WINDS WILL CONTINUE TO DIMINISH AND RELATIVE HUMIDITIES WILL INCREASE THIS EVENING...THUS THE RED FLAG WARNING WILL BE ALLOWED TO EXPIRE. $$