INTERAGENCY FIRE WEATHER CENTER – PREDICTIVE SERVICES UNIT

 

TUESDAY, JUNE 28, 2016

SOUTHERN CALIFORNIA GEOGRAPHICAL AREA COORDINATION CENTER

RIVERSIDE, CALIFORNIA

***Isolated thunderstorms over the mountains and deserts through Wednesday***

***Hot away from the coastal areas through Wednesday***

A weak disturbance over the area will bring isolated showers and thunderstorms to the Sierra and to the mountains and deserts of Southern California through this evening.  The disturbance will move to the northeast ending the shower and thunderstorm threat across Southern California Wednesday, but isolated showers and thunderstorms will continue across Central California from the Sierra eastward through Wednesday evening.  Strong high pressure over Utah will maintain temperatures that are 5 to 15 degrees above normal through Wednesday, with mid 80s to mid 90s across the mountains and mid 90s to 108 in the valleys.  Minimum humidity will be mainly between 12% and 25% away from the coastal areas through Wednesday.  A weak Pacific trough will move over the West Coast Thursday through this weekend bringing significant cooling to the region.  Temperatures will be near normal Friday through this weekend.  There will be widespread minimum humidity in the single digits and teens above and inland from the marine layer Thursday through this weekend as a dry southwest flow aloft develops.  The marine layer will deepen to around 2,000 feet by Friday which will allow morning low clouds and fog to push into most coastal valley locations.  South to west afternoon winds of 15 to 25 mph with gusts to 40 mph will surface across the desert passes Thursday through this weekend.

 

There will be a high risk for large fire across the Central and Southern Sierra today due to thunderstorms with some dry lightning strikes.  These two PSAs are where most of the lightning is expected away from the desert areas today.  There will also be an elevated risk for large fire across the Southern California Mountains north of San Diego County today due to lightning, but thunderstorms will be very isolated so a “High Risk” day was not added.  Downdraft winds from any thunderstorm will likely cause rapid rates of spread and long range spotting on any new ignition that gets past its initial attack phase.  Very dry fuels along with hot temperatures will allow for moderate to rapid rates of spread on any new ignition across the valley and foothill areas during the peak heating hours of the afternoons through Wednesday.  The potential for large fire will decrease significantly Thursday through this weekend as temperatures cool across the area and the marine layer deepens over the coastal areas.  The best chance for large fire activity starting Thursday will be over the Grapevine and the Owens Valley where gusty southerly winds will develop in the afternoons combined will single digit relative humidity.  Expect moderate to heavy initial attack activity through Wednesday and then light to moderate IA activity Thursday through this weekend.

 

For addition fuels and weather information, including the Santa Ana Wildfire Threat Index, please visit:

 

http://gacc.nifc.gov/oscc/predictive/weather/index.htm