Very warm weather is expected through Saturday as high pressure builds into the region, where highs will be up to 20 degrees above normal with light offshore winds. The high will weaken by Sunday into Monday, increasing onshore flow and providing some cooling to the region. A ridge will rebuild over the area by the middle of next week, which will lead to warm and drier weather.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Subtropical moisture is streaming in from the south and the southwest via satellite imagery. These highs clouds will continue to move over the region throughout the day, clearing from NW to SE overnight. Cloud cover will help limit high temperatures today with 70s in the inland valleys and lower deserts with 50s and lower 60s for areas over 5,000 feet. Hi-res models show increasing offshore winds through passes with winds gusting near 20-30 MPH by this evening through Thursday.
A ridge of high pressure will continue to build into the area Thursday through Saturday. This will bring very warm temperatures to Southern California as skies clear out. Chances are moderate to high to see high temperatures reaching 80 degrees for western valleys to areas within 10 miles of the coast, as well as the Coachella Valley. Breezy offshore flow will contribute to this warming as the ridge builds in through Saturday. By Friday and Saturday, very warm weather will occur over the area with temperautres locally over 15 degrees above normal. We will continue to refine the forecast, but model guidance has shown a slight warming trend for these days with around a 30-50% chance of seeing highs over 85 degrees for parts of the inland SD County valleys, northern Orange County and western parts of the Inland Empire. Though it is wintertime and the peak of the heat will not last long in duration, make sure to check on neighbors. Temperatures will peak in the afternoon with low temperatures dropping off into the 50s and 60s for lower elevations. Offshore winds will be fairly weak through this period, but highest for passes/foothills across SD/RIV Counties on Friday afternoon with gusts 25-35 MPH.
High pressure will weaken by Sunday and Monday. This will increase onshore flow and lower temperatures around 5 degrees west of the mountains. The cooling will reach mountain areas by Monday. Monday will be the coolest day of the week along and west of the mountains with highs in the upper 60s near the coast with low to mid 70s in the valleys, and 50s/60s across higher elevations.
Another ridge of high pressure will build into California by Tuesday through the middle of next week. Models are in fair agreement of this ridge moving over the region and increasing temperatures yet again, where NBM shows a subtle warming trend by next Tuesday into Wednesday. By this time, the ridge may amplify all the way up into British Columbia/Alberta, Canada. A weak area of low pressure moving into the Pacific Northwest may drift over the ridge and drop southward into the Greab Basin by the middle of next week, which would create an "inslider scenario". This would lead to increased Santa Ana winds over our region with more warm and dry weather.
282030z, VFR conditions with SCT-BKN high clouds AOA 20000 feet MSL through this evening, clearing out late tonight into Thursday morning. Afterwards, generally sunny skies. An uptick in northerly winds over the mountains after 06z, increasing through 18z. There will be some spillover into the Inland Empire with wind gusts up to 15-20kts after 16z.
No hazardous marine conditions are expected through Monday.
Ca, None. PZ, None.
