Red Flag Warning
Severity: Severe
Significant threat to life or property
Weather Event Onset
8:00 PM (PST), December 9
Description
…PARTICULARLY DANGEROUS SITUATION (PDS) RED FLAG WARNING IN EFFECT FROM 8 PM TONIGHT UNTIL 2 PM TUESDAY DUE TO DAMAGING SANTA ANA WINDS AND VERY LOW HUMIDITIES FOR THE FOLLOWING AREAS: SAN GABRIEL MOUNTAINS/ SANTA MONICA MOUNTAINS/ SANTA CLARITA VALLEY/ CALABASAS/ VENTURA COUNTY COASTS AND VALLEYS/ WESTERN SAN FERNANDO VALLEY — AND RED FLAG WARNINGS IN EFFECT FOR ALL OTHER TIMES UNTIL 6 PM WEDNESDAY IN THESE SAME AREAS…
…PARTICULARLY DANGEROUS SITUATION (PDS) RED FLAG WARNING IN EFFECT FROM 8 PM TONIGHT UNTIL 10 AM WEDNESDAY DUE TO DAMAGING SANTA ANA WINDS AND VERY LOW HUMIDITIES FOR THE FOLLOWING AREAS: SANTA SUSANA MOUNTAINS– AND RED FLAG WARNINGS IN EFFECT FOR ALL OTHER TIMES UNTIL 6 PM WEDNESDAY IN THIS SAME AREA…
…PARTICULARLY DANGEROUS SITUATION (PDS) RED FLAG WARNING IN EFFECT FROM 8 PM TONIGHT UNTIL 2 PM TUESDAY DUE TO DAMAGING SANTA ANA WINDS AND VERY LOW HUMIDITIES FOR THE FOLLOWING AREAS: VENTURA COASTAL PLAIN (ESPECIALLY FOOTHILLS)/ MALIBU COAST — AND RED FLAG WARNINGS IN EFFECT FOR ALL OTHER TIMES FROM 2 PM MONDAY UNTIL 2 PM WEDNESDAY IN THESE SAME AREAS…
…RED FLAG WARNING IN EFFECT UNTIL 6 PM WEDNESDAY FOR VENTURA MOUNTAINS, I5 CORRIDOR, EASTERN SAN FERNANDO VALLEY, AND SAN GABRIEL VALLEY DUE TO GUSTY SANTA ANA WINDS AND VERY LOW HUMIDITIES…
…RED FLAG WARNING IN EFFECT FROM 10 PM TONIGHT UNTIL 10 PM TUESDAY FOR THE SAN LUIS OBISPO COUNTY MOUNTAINS DUE TO GUSTY EAST TO SOUTHEAST WINDS AND VERY LOW HUMIDITIES…
…RED FLAG WARNING IN EFFECT FROM 8 PM TONIGHT UNTIL 2 PM TUESDAY FOR THE CHANNEL ISLANDS AND PALOS VERDES DUE TO GUSTY SANTA ANA WINDS AND VERY LOW HUMIDITIES…
***THIS IS A PARTICULARLY DANGEROUS SITUATION (PDS) FOR MANY AREAS OF LOS ANGELES AND VENTURA COUNTIES ***
A strong, widespread, and long duration Santa Ana event will bring widespread critical to extremely critical fire weather conditions to many areas of Los Angeles and Ventura counties through Wednesday. This will be a PARTICULAR DANGEROUS SITUATION (PDS) Red Flag Warning event in many areas, with the combination of a strong offshore pressure gradient (LAX-Daggett peaking at -8 to -9 mb), strong cold air advection, and moderate upper level wind support.
As surface high pressure builds into the Great Basin, Santa Ana winds are expected to increase through the afternoon, then peak tonight into Tuesday. A marine layer cloud presence this morning may delay the onset of offshore winds across portions of the coast and coastal valleys by a few hours from what was expected yesterday. Offshore winds are expected to diminish some by Wednesday, but very dir will persist. With the strong likelihood of widespread single digit humidities with this event, there is high confidence for a long duration Red Flag event. In addition, there is high confidence of PDS Red Flag Warning conditions late this evening through Tuesday, as damaging wind gusts of 60 to 80 mph will likely overlap with single digit humidities across many of the windier mountain and foothill areas, and with gusts of 40 to 65 mph across most wind prone coastal and valley areas of Los Angeles and Ventura counties. With the threat of damaging wind gusts in these windier corridors, there will be an increased risk for downed trees and powerlines, along with power outages. The hardest hit areas will likely be the San Gabriels, Santa Susanas, western Santa Monicas into Malibu, Ventura county valleys (especially Simi Valley and Moorpark), western San Fernando Valley (especially Highway 118/210 corridors from Porter Ranch to San Fernando), and the hills above Camarillo into east Ventura. Due to the expected long duration of dangerous fire weather conditions and critically dry fuels, there is an increased risk for any new ignitions to have very rapid fire spread and extreme fire behavior (including long range spotting). As a result, there is the increasing threat for fire weather conditions to rival other historical fires in recent times including the Mountain and Thomas Fires. Dry offshore conditions will likely persist into Thursday morning, with a return of onshore flow and some humidity recovery in the afternoon.
* WINDS…Santa Ana winds expected to increase sharply this evening and persist through early Tuesday afternoon. During the peak of the event, wind speeds of 25 to 35 mph with gusts of 45 to 60 mph can be expected, with the strongest winds focused across higher terrain.
* RELATIVE HUMIDITY…Humidities are expected to lower to around 15 percent in many areas by this evening, with widespread humidities of 5 to 10 percent likely by Tuesday.
* IMPACTS…If fire ignition occurs, conditions are favorable for large fires with very rapid fire spread, extreme fire behavior, and long range spotting, which would threaten life and property. There is also the risk of locally damaging winds.
Action Recommended
Make preparations per the Description.
Urgency
Take action within next hour.
Affected Area
Ventura
Issued By
National Weather Service
Red Flag Warning
Severity: Severe
Significant threat to life or property
Weather Event Onset
1:40 PM (PST), December 9
Description
…PARTICULARLY DANGEROUS SITUATION (PDS) RED FLAG WARNING IN EFFECT FROM 8 PM TONIGHT UNTIL 2 PM TUESDAY DUE TO DAMAGING SANTA ANA WINDS AND VERY LOW HUMIDITIES FOR THE FOLLOWING AREAS: SAN GABRIEL MOUNTAINS/ SANTA MONICA MOUNTAINS/ SANTA CLARITA VALLEY/ CALABASAS/ VENTURA COUNTY COASTS AND VALLEYS/ WESTERN SAN FERNANDO VALLEY — AND RED FLAG WARNINGS IN EFFECT FOR ALL OTHER TIMES UNTIL 6 PM WEDNESDAY IN THESE SAME AREAS…
…PARTICULARLY DANGEROUS SITUATION (PDS) RED FLAG WARNING IN EFFECT FROM 8 PM TONIGHT UNTIL 10 AM WEDNESDAY DUE TO DAMAGING SANTA ANA WINDS AND VERY LOW HUMIDITIES FOR THE FOLLOWING AREAS: SANTA SUSANA MOUNTAINS– AND RED FLAG WARNINGS IN EFFECT FOR ALL OTHER TIMES UNTIL 6 PM WEDNESDAY IN THIS SAME AREA…
…PARTICULARLY DANGEROUS SITUATION (PDS) RED FLAG WARNING IN EFFECT FROM 8 PM TONIGHT UNTIL 2 PM TUESDAY DUE TO DAMAGING SANTA ANA WINDS AND VERY LOW HUMIDITIES FOR THE FOLLOWING AREAS: VENTURA COASTAL PLAIN (ESPECIALLY FOOTHILLS)/ MALIBU COAST — AND RED FLAG WARNINGS IN EFFECT FOR ALL OTHER TIMES FROM 2 PM MONDAY UNTIL 2 PM WEDNESDAY IN THESE SAME AREAS…
…RED FLAG WARNING IN EFFECT UNTIL 6 PM WEDNESDAY FOR VENTURA MOUNTAINS, I5 CORRIDOR, EASTERN SAN FERNANDO VALLEY, AND SAN GABRIEL VALLEY DUE TO GUSTY SANTA ANA WINDS AND VERY LOW HUMIDITIES…
…RED FLAG WARNING IN EFFECT FROM 10 PM TONIGHT UNTIL 10 PM TUESDAY FOR THE SAN LUIS OBISPO COUNTY MOUNTAINS DUE TO GUSTY EAST TO SOUTHEAST WINDS AND VERY LOW HUMIDITIES…
…RED FLAG WARNING IN EFFECT FROM 8 PM TONIGHT UNTIL 2 PM TUESDAY FOR THE CHANNEL ISLANDS AND PALOS VERDES DUE TO GUSTY SANTA ANA WINDS AND VERY LOW HUMIDITIES…
***THIS IS A PARTICULARLY DANGEROUS SITUATION (PDS) FOR MANY AREAS OF LOS ANGELES AND VENTURA COUNTIES ***
A strong, widespread, and long duration Santa Ana event will bring widespread critical to extremely critical fire weather conditions to many areas of Los Angeles and Ventura counties through Wednesday. This will be a PARTICULAR DANGEROUS SITUATION (PDS) Red Flag Warning event in many areas, with the combination of a strong offshore pressure gradient (LAX-Daggett peaking at -8 to -9 mb), strong cold air advection, and moderate upper level wind support.
As surface high pressure builds into the Great Basin, Santa Ana winds are expected to increase through the afternoon, then peak tonight into Tuesday. A marine layer cloud presence this morning may delay the onset of offshore winds across portions of the coast and coastal valleys by a few hours from what was expected yesterday. Offshore winds are expected to diminish some by Wednesday, but very dir will persist. With the strong likelihood of widespread single digit humidities with this event, there is high confidence for a long duration Red Flag event. In addition, there is high confidence of PDS Red Flag Warning conditions late this evening through Tuesday, as damaging wind gusts of 60 to 80 mph will likely overlap with single digit humidities across many of the windier mountain and foothill areas, and with gusts of 40 to 65 mph across most wind prone coastal and valley areas of Los Angeles and Ventura counties. With the threat of damaging wind gusts in these windier corridors, there will be an increased risk for downed trees and powerlines, along with power outages. The hardest hit areas will likely be the San Gabriels, Santa Susanas, western Santa Monicas into Malibu, Ventura county valleys (especially Simi Valley and Moorpark), western San Fernando Valley (especially Highway 118/210 corridors from Porter Ranch to San Fernando), and the hills above Camarillo into east Ventura. Due to the expected long duration of dangerous fire weather conditions and critically dry fuels, there is an increased risk for any new ignitions to have very rapid fire spread and extreme fire behavior (including long range spotting). As a result, there is the increasing threat for fire weather conditions to rival other historical fires in recent times including the Mountain and Thomas Fires. Dry offshore conditions will likely persist into Thursday morning, with a return of onshore flow and some humidity recovery in the afternoon.
* WINDS…Santa Ana winds expected to increase sharply this afternoon, then peak tonight into Tuesday. when speeds of 25 to 40 mph with gusts of 40 to 65 mph common across coastal and valley areas. Some of the windier foothills and mountains will likely see wind speeds of 30 to 50 mph with damaging wind gusts in the 60 to 80 mph range during the peak of the event tonight into Tuesday. Some of the highest wind areas will likely be the San Gabriels, Santa Susanas, western Santa Monicas into Malibu, Ventura county valleys (especially Simi Valley and Moorpark), and western San Fernando Valley (especially Highway 118/210 corridors from Porter Ranch to San Fernando). Offshore winds are expected to diminish some by Wednesday, with gusts mostly in the 20 to 40 mph range in the morning.
* RELATIVE HUMIDITY…Humidities are expected to lower to around 15 percent in many areas by this afternoon or early evening, with widespread humidities of 5 to 10 percent likely later this evening into Tuesday, and persisting into Wednesday, with isolated readings as low as 2 percent likely.
* IMPACTS…If fire ignition occurs, conditions are favorable for large fires with very rapid fire spread, extreme fire behavior, and long range spotting, which would threaten life and property. There is also the risk of damaging winds including downed trees and power lines, as well as power outages.
Action Recommended
Make preparations per the Description.
Urgency
Take action within next hour.
Issued By
National Weather Service