A Red Flag Warning, more appropriately known as a Fire Weather Warning, is a forecast warning issued by the United States National Weather Service to inform area firefighting and land management agencies that conditions are ideal for wildland fire combustion, and rapid spread. After drought conditions, when humidity is very low, and especially when there are high or erratic winds which may include lightning as a factor, the Red Flag Warning becomes a critical statement for firefighting agencies. These agencies often alter their staffing and equipment resources dramatically to accommodate the forecast risk. To the public, a Red Flag Warning means high fire danger with increased probability of a quickly spreading vegetation fire in the area within 24 hours.
The weather criteria for fire weather watches and red flag warnings vary with each Weather Service Office’s warning area based on the local vegetation type, topography, and distance from major water sources. They usually include the daily vegetation moisture content calculations, expected afternoon high temperature, afternoon minimum relative humidity and daytime wind speed.
Outdoor burning bans may also be proclaimed by local law and fire agencies based on Red Flag Warnings.
A separate but less imminent forecast may include a Fire Weather Watch, which is issued to alert fire and land management agencies to the possibility that Red Flag conditions may exist beyond the first forecast period (12 hours). The watch is issued generally 12 to 48 hours in advance of the expected conditions, but can be issued up to 72 hours in advance if the NWS agency is reasonably confident. The term “Fire Weather Watch” is headlined in the routine forecast and issued as a product. That watch then remains in effect until it expires, is canceled, or upgraded to a Red Flag Warning.
URGENT - FIRE WEATHER MESSAGENATIONAL WEATHER SERVICE SEATTLE WA348 PM PDT SAT JUL 25 2009...ONE OF THE MOST CRITICAL FIRE WEATHER SETUPS IN YEARS FORWESTERN WASHINGTON....AN UPPER LEVEL LOW PRESSURE CENTER CONTINUES TO SPIN OVERCENTRAL WASHINGTON THIS AFTERNOON.WAZ653-654-656>659-661-662-261200-/O.CON.KSEW.FW.W.0003.000000T0000Z-090726T1200Z/STRAIT OF JUAN DE FUCA AND NORTHWEST INTERIOR LOWLANDS-CENTRAL AND SOUTH PUGET SOUND LOWLANDS-WEST SLOPES OF THE NORTH CASCADES-WEST SLOPES OF THE CENTRAL CASCADES-NORTH CASCADES-CENTRAL CASCADES-EAST PORTION OF THE OLYMPIC MOUNTAINS-EAST PORTION OF NORTH CASCADES NATIONAL PARK/LAKE CHELAN NATIONALRECREATIONAL AREA-348 PM PDT SAT JUL 25 2009...RED FLAG WARNING REMAINS IN EFFECT UNTIL 5 AM PDT SUNDAY...A RED FLAG WARNING REMAINS IN EFFECT UNTIL 5 AM PDT SUNDAY.AN UPPER LEVEL LOW PRESSURE CENTER CONTINUED TO SPIN OVER CENTRALWASHINGTON ON SATURDAY AFTERNOON. THUNDERSTORMS HAD ALREADYDEVELOPED OVER SOUTHERN BRITISH COLUMBIA AND WILL MOVE SOUTHWESTINTO WESTERN WASHINGTON LATER THIS AFTERNOON AND TONIGHT AS THEYTRACK AROUND THE PERIPHERY OF THE UPPER LOW. THE STORMS WILLFIRST REACH THE NORTH CASCADES AND NORTH INTERIOR...THEN SPREADSOUTHWEST AND SOUTH THIS EVENING THROUGH THE CENTRAL CASCADES ANDTHE PUGET SOUND LOWLANDS. THUNDERSTORMS COULD ALSO CLIP THE EASTSLOPES OF THE OLYMPIC MOUNTAINS.SOME OF THESE THUNDERSTORMS ARE EXPECTED TO BE UNUSUALLY PROLIFICLIGHTNING PRODUCERS. GIVEN THE EXPECTED ABUNDANCE OF LIGHTNINGAND CRITICALLY DRY FUEL STATES...MULTIPLE FIRE IGNITIONS AREEXPECTED.ONE THING THAT MAKES THIS ROUND OF LIGHTNING SO CRITICAL IS THATIT WILL BE FOLLOWED UP ON SUNDAY AND MONDAY BY A BUILDING ANDPROLONGED HEAT WAVE. UNLIKE WESTERN WASHINGTON`S TYPICALLIGHTNING PATTERN IN WHICH LIGHTNING IS FOLLOWED BY COOL MARINEAIR...THIS LIGHTNING PATTERN WILL BE FOLLOWED INSTEAD BYHOT...DRY AND INCREASINGLY UNSTABLE WEATHER ON SUNDAY...MONDAYAND TUESDAY. THIS WILL MAKE HOLDOVER AND SLEEPER FIRES A GREATCONCERN IN THE DAYS TO COME.PLEASE RELAY THIS MESSAGE TO FIRE AND ENGINE CREWS IN THE FIELD.PRECAUTIONARY/PREPAREDNESS ACTIONS...PEOPLE WHO WILL BE OUTDOORS FROM THIS AFTERNOON THROUGH TONIGHTSHOULD BE AWARE OF THE SEVERE LIGHTNING THREAT AND THE ENHANCED THREATOF WILDFIRES. MAKE AN EXTRA EFFORT TO FULLY EXTINGUISH CAMPFIRESAND REPORT ANY NEW WILDFIRES WHICH YOU MIGHT SEE. FIREFIGHTINGAGENCIES SHOULD BE READY FOR SEVERAL BUSY DAYS OF INITIAL ATTACK.A RED FLAG WARNING IS ISSUED WHEN DRY LIGHTNING OR THECOMBINATION OF STRONG WINDS AND LOW HUMIDITIES ARE IMMINENT OROCCURRING.&&$$HANERWEATHER.GOV/SEATTLE
