A cooling trend through Saturday, with high temperatures 10 to 15 degrees below average for inland areas to as much as 20 degrees below average for the higher elevations of the mountains by the weekend. The marine layer will deepen with night and morning coastal low clouds and fog extending onto the lower coastal slopes of the mountains for today and Thursday, then farther onto the coastal mountain slopes for Friday and Saturday. There will be stronger onshore flow with gusty southwest to west winds for the mountains and deserts each late afternoon and evening through Saturday. There is also a slight chance for mostly light showers for late Friday night into Saturday evening. Then dry with a warming trend for Sunday through Tuesday.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Update: The models have been rather consistent with the timing of a shortwave moving over the region through the early part the weekend, which will bring a chance of light rain and/or drizzle to portions of the coastal and inland areas, as well as provide strong and gusty winds for the mountains and deserts, particularity those locations most prone to gap flow winds, such as the passes and Coachella Valley. The high res guidance reflects that the best chance of any measurable precipitation will be during the afternoon on Saturday, with gradual clearing going into the late evening hours, and then drying out by Sunday. Saturday still appears to be the coolest day, with highs generally anywhere between 10 to 20 degrees below the seasonal average for most locations. Models have also remained consistent with showing slight ridging and a warming trend through the mid part of next week. Onshore flow will also remain persistent, and keep the marine layer redevelopment during the overnight hours continuing through the mid part of next week as well.
(Previous discussion submitted at 139 PM):
Satellite shows that extensive cloud cover remains with slow clearing from south to north. Parts of Riverside and Orange counties will struggle to clear today, but clouds should retreat to the coast by the late afternoon. Sunny skies and increasing winds out of the west over the next several hours, calming later tongiht. Heights fall through Saturday as a trough off the coast of Canada becomes a cutoff low and moves southward into California. With the falling heights, the marine layer deepens the next few mornings, making it further inland each day and allowing morning drizzle to occur, especially for the coastal areas and valleys. Temperatures also respond, with highs falling substantially by Friday and Saturday, generally 5-20 degrees below normal for the end of April. Gusty west winds develop each afternoon and evening as the gradient tightens this week, with gusts up to 40 mph in the deserts and mountains and localized areas of gusts up to 55 mph through the mountain passes, peaking both Friday and Saturday afternoons. Some areas of blowing dust will be possible, especially in the deserts.
The latest model runs have slowed the progression of the aforementioned low and brought it a smidge further south on Saturday, indicating slightly higher precipitation chances than previous runs, now around 20-25% for the mountains. While POPs have increased, QPF unfortunately remains fairly low with limited moisture and energy to tap in to. Right now the best chances for accumulating rainfall will be for the areas further north, especially the higher terrain, where up to 0.10-0.15" is possible through Saturday night.
As the low moves up into Nevada on Sunday, highs warm a few degrees but will remain well below normal. By Monday, weak upper level ridging starts to build in, with temperatures quickly warming through mid week and highs return to near or slightly above normal by Tuesday.
240330z. Coasts/Valleys/Coastal Mountain Slopes, Clouds continue to spread inland this evening and tonight based at 2000-3000 ft MSL, and will fill the coastal basin by early Thursday morning, bringing patchy DZ. Clouds clearing again 16-19Z Friday, though locally BKN near the coast into the afternoon. Clouds 2500-3500 ft MSL spreading inland again to a similar inland extant after 02Z Fri.
Otherwise, Mostly clear through Wednesday.
No hazardous marine conditions are expected through Sunday.
Ca, None. PZ, None.
