Scattered showers will slowly move southeastward across the area through the night. 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,
.Evening Update,
Light showers continue to stream over the area with hourly rain rates generally under one quarter of an inch. Clearing can be seen via satellite from Santa Barbara to Malibu, which will continue to progress eastward overnight. A cool day will be had on Saturday with high temperatures up to 10 degrees below normal with highs in the 50s to low 60s across the high desert and west of the mountains. Drier and warmer weather remains in the forecast for early next week with a potentially more active weather pattern returning as we head into the New Year.
.Previous Discussion (123 PM Friday),
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. 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.
270430z. Coasts/Valleys, -SHRA across the coastal basin is currently producing intermittent MFVR to locally IFR cigs/vis. Most of the precipitation and associated cig/vis restrictions will exit the coastal basin by 08Z with only isolated -SHRA, thereafter. SCT clouds based 3000-6000 ft MSL through the afternoon on Sat with isolated SHRA near the coastline 15-19Z.
.Mountains/Deserts, Widespread mid level clouds based 4000-6000 ft MSL along with RA in the mtns and SCT -SHRA in the deserts will slowly exit the region through 10Z Sat. Clouds will linger along coastal slopes through 18Z. Southwesterly winds turning westerly 06- 09Z and gusting 25-35 knots and downwind of desert slopes through 18Z. Locally higher gusts through mountain passes. Mod up/downdrafts downwind of the mountains through 18Z.
Northwest winds gusting near 20 kts will 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 early 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.
PZ, None.
