Bands of showers with a slight chance of embedded thunderstorms will slowly move southeastward across the area through this evening. Drying will develop over the weekend and continue into early next week, with periods of weak to moderate strength gusty Santa Ana winds for Sunday through Tuesday. Slight warming will accompany the offshore flow for Monday and Tuesday. A low pressure system from the southwest could bring a return of precipitation for Wednesday through Friday.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Extensive troughing over the west coast of the US, with embedded shortwave troughs, will continue to bring precipitation to SoCal through tonight. Bands of showers with a slight chance of embedded thunderstorms, associated with a frontal boundary, will slowly move southeastward across the area today through this evening. The convective elements within the band are moving to the northeast at about 30 mph with the steering flow aloft. This pattern of flow will result in orographic enhancement of rainfall amounts on the coastal mountain slopes - especially the San Bernardino Mountains. Showers could linger in San Diego County overnight after the passage of the frontal boundary when the winds become northwesterly and low level convergence downstream of offshore islands produces convection in the cold air behind the front.
As the low pressure trough moves inland and a high pressure ridge builds over the PAC Northwest, a drying trend develops for the weekend into early next week. For Sunday through Tuesday, weak to moderate offshore flow develops. Northeast Santa Ana winds gusting to 35-45 mph in and below the mtn passes and canyons are expected for Sunday and Monday.
By Monday, a closed upper low develops to our southwest while the high pressure ridge builds to our north. This will likely bring a warming trend for Sunday- Wednesday. Tuesday will likely be the warmest day with temperatures in the 70s (as much as 5-6 degrees above averages) west of the mtns.
For the middle to the end of next week, A low pressure system from the Gulf of Alaska will approach the west coast, displacing the high pressure ridge and drawing the closed low to our southwest northeastward into the mean flow over SoCal. There are significant differences among numerical model solutions with respect to how this pattern will evolve but an increasing number of ensemble members are indicating the possibility of precipitation for SoCal between next Wednesday and Friday. At this time, precipitation amounts are highly uncertain.
See the HYDROLOGY discussion for precipitation details.
Additional rainfall through tonight for Orange and southwestern San Bernardino Counties is expected to range from 0.50 to 0.75 inch near the coast to 1 to 2 inches in the San Bernardino County mountains, locally up to 3 inches on the coastal slopes of the eastern San Gabriel Mountains. Amounts will decrease from north to south with around 0.25-0.35 inch expected over far southern San Diego County.
By Saturday morning, high-resolution models indicate a 50-70 percent probability of exceeding 2 inches of rain in the San Bernardino Mountains and about a 20 percent chance in the Santa Ana Mountains.
The snow level is now above 7500 feet, but will fall to around 4500 feet by late tonight. Snowfall in the San Bernardino County mountains of 1 to 3 inches is possible down to around 7000 feet with snowfall of 8 to 12 inches above 8000 feet.
Preliminary precipitation estimates for next Wed through Fri: 0.25"-0.50" in the low deserts, 0.40"-0.75" inch in the high deserts, 1.25"-1.60" in the coastal areas and valleys to 2-3 inches on the coastal mtn slopes.
261815z. Coasts/Valleys, Fairly widespread mid level clouds around 5000ft MSL currently stretching from Orange County associated with bands of largely light rainfall are present with more scattered clouds at 1500-2500ft MSL. This could will occasionally become BKN to provide instances of MVFR CIGs, primarily in areas of more steady/moderate rainfall. The batches of RA associated with a main band of rainfall will occasionally bring VIS down to 2-4SM with any heavier rain. This main band of RA to locally +RA is currently draped across Orange County into the western Inland Empire, and will slowly push eastward into the afternoon, with RA chances eventually decreasing by 03-06z Saturday. Low/mid level cloud cover largely becomes FEW-SCT overnight, but become SCT-BKN again around 15z Saturday with a few stray showers across the coastal areas 15-20z.
Gusty southerly winds up to 20kt are possible with moderate up/downdrafts downwind of the Santa Anas into the Inland Empire through 23z today through 01z Saturday.
.Mountains/Deserts, Widespread mid level clouds with bases around 5000ft MSL. Winds continue to gradually decrease today though westerly-northwesterly winds persist for the desert slopes of the mountains into Saturday afternoon. Wind gusts up to 25-30 knots expected, locally higher through mountain passes, with mod up/downdrafts near the mountains.
South to southwest winds strengthen again today with gusts near 20 knots at times. Winds will then turn northwest and gradually decrease late tonight into Saturday. Otherwise, no hazardous marine weather expected through Wednesday.
Westerly swell (250-270 degrees) will lead to surf heights increasing to 5 to 8 feet through Saturday. Highest surf is expected for west-facing beaches. A High Surf Advisory remains in effect until late Saturday morning.
Ca, High Surf Advisory until 11 AM PST Saturday for Orange County Coastal Areas-San Diego County Coastal Areas.
Flood Watch until 4 PM PST this afternoon for Apple and Lucerne Valleys-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire.
PZ, None.
