A deep marine layer; gusty winds in the mountains and deserts; and cooler conditions will prevail through Friday. Patchy drizzle or light rain is expected each night and morning west of the mountains. Gusty southwest to west winds will peak each afternoon and evening in the mountains and deserts through Friday. Winds will weaken through the weekend. Drier and warmer with a shallower marine layer expected early next week.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
.Evening Update, High clouds are streaming in over the high desert as low clouds fill in much of the coastal basin this evening. Latest HRRR model guidance indicates drizzle and light showers will develop mainly after midnight, lasting until the mid morning hours. Winds have been gusty this evening as the trough axis moves over Southern California. Peak wind gusts have been mainly near 30-40 MPH across mountains and deserts, with highest gusts near 60 MPH in the San Gorgonio Pass and near In-Ko-Pah in San Diego County.
Graypril will continue for much of the day on Thursday for those west of the mountains, especially away from the coast per latest HREF model guidance. The deep marine layer will maintain itself into Friday, so the chance for drizzle and light showers will once again occur Thursday night into Friday morning. Winds will also continue to be gusty across the mountains into the deserts on Thursday and Friday as well. Friday will see the strongest winds with these areas seeing peak wind gusts 40-55 MPH. Not all is lost, as a brighter and warmer weekend is in store!
.Previous Discussion (133 PM PDT Wednesday), Low clouds are expected to fill in the coastal basin again tonight into Thursday morning. Deep marine layer moisture combined with lift from a low pressure system passing through Southern California and Northern Baja will generate areas of drizzle and light rain this evening and overnight. The greatest coverage is expected to be in the coast and valleys in San Diego County and along the coastal mountain slopes. Any accumulations for the coast and valleys will be light, with 0.10 inches or less expected. On the coastal mountain slopes, around 0.25 inch is expected. Marine layer low clouds may become patchier Thursday night into Friday morning, but areas of drizzle or light rain are still possible. Dry conditions expected for the weekend into early next week.
Gusty southwest to west winds are expected in the mountains and deserts through Friday. Peak winds gusts will be 50 to 65 mph. Gusts could locally reach up to 75 mph through the San Gorgonio Pass. Winds will peak each afternoon and evening. Winds will gradually decrease in the the weekend, with weaker winds expected early next week.
Cooler conditions expected for inland areas Thursday, with a few degrees of warming on Friday for the coast. High temperatures will be as much as 10 to 15 degrees below average on Thursday for the mountains and valleys. A warming trend is expected for Saturday through Monday with not much change on Tuesday. Weak high pressure aloft is expected to prevail but there are some model differences for early in the week which would impact the strength of the onshore flow and the depth of the marine layer. This uncertainty creates greater spread of the high temperature forecasts for locations in the coast and valleys. If the warming develops, high temperatures would be near average for most locations on Sunday with high temperatures on Monday and Tuesday 3 to 7 degrees above average.
250400z, Coast/Valleys, Widespread BKN/OVC stratus will prevail through 18Z Thu with bases 2000-4000 ft MSL and tops to 6500 ft MSL and with higher terrain obscured. Local VIS 3-5 miles will occur below the clouds in -DZ/-SHRA, mainly 09Z-18Z Thu. SCT/BKN stratus will prevail with bases 2500-5000 ft MSL 18Z Thu-03Z Fri, with increasing stratus again after 03Z Fri.
Mountains/Deserts, Areas of terrain obscurations will continue at times along the coastal mountain slopes through Thu evening with cloud tops to 7500 ft MSL and (09Z-18Z Thu) areas of -DZ/-SHRA. Areas of west winds with surface gusts 30-50 kt will occur from the mountain crests east through the mountain slopes and into the deserts through Thu evening. VIS will be unrestricted on the desert slopes/deserts.
No hazardous marine conditions are expected through Thursday night. Stronger winds and choppy seas arrive Friday morning and continue into Saturday morning, likely generating hazardous conditions, especially in the outer waters. There is a period Friday night (mainly mid-evening to a little after midnight) when there is around a 25 percent chance of gale force winds near San Clemente Basin Buoy. There is a gale watch in effect from 5 PM Friday through 3 AM Saturday for this possibility, though there is high confidence of winds reaching Small Craft Advisory strength.
Ca, Wind Advisory until 11 PM PDT Friday for Apple and Lucerne Valleys-Coachella Valley-Riverside County Mountains-San Bernardino County Mountains-San Diego County Deserts-San Diego County Mountains-San Gorgonio Pass Near Banning.
PZ, Gale Watch from Friday afternoon through late Friday night for Waters from San Mateo Point to the Mexican Border Extending 30 to 60 nm out including San Clemente Island.
