Near average temperatures today with below average temperatures expected Monday through midweek. Low clouds will spread into the valleys each night and morning, lingering into the afternoon at times along the coast. Increased westerly winds expected Tuesday through potentially Thursday for the mountains and deserts. Patchy drizzle or light rain possible west of the mountains each night and morning from Monday night through Thursday morning.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Marine layer low clouds have filled in across the coastal basin this morning and have even spread into the Cajon Pass. Further inland skies are clear. A weak upper level low off the coast of Southern CA will move eastward today, moving overhead this evening into Monday morning. This will lead to minor cooling with high temperatures near to slightly below normal. The marine layer deepens further into Monday morning, potentially producing spotty light drizzle west of the mountains. Limited clearing is expected for the coastal areas today, and the coastal areas and far western valleys on Memorial Day. The cooling trend continues into Memorial Day as well with high temperatures around 3-5 degrees below normal for the mountains westward, and near normal in the deserts.
Ensembles continue to converge on a solution for the next upper level low midweek. This low is forecast to move through the Pac NW on Tuesday, slowly moving south through CA/NV into Thursday. This will bring more substantial cooling with high temperatures 10-20 degrees below normal inland, with the greatest departure from normal in the mountains. The marine layer depth increases to around 5000 ft, and with large-scale forcing with the trough should be plenty sufficient to produce drizzle along and west of the mountains Tuesday through Thursday during the nights and mornings. There is around a 10% chance of accumulating precipitation, though any accumulations would be light (less than 0.10"). This trough will also produce gusty onshore winds in the mountains and deserts, strongest on Tuesday and Wednesday during the afternoons into late nights. Wind gusts will generally be around 35-45 mph in these areas, with isolated gusts to 60 mph through the passes.
The upper low lifts out to the northeast on Friday, followed by generally weak troughing over the western US into the weekend. This will allow for temperatures to gradually increase to around normal next weekend. Night and morning low clouds continue (it is May Gray after all), but with less inland extent and better clearing during the day.
241200z, Coast/Valleys, Low clouds based 1800-2300 ft MSL have filled in across the coastal basin this morning through to the mountain slopes. Locally reduced VIS 4-6SM in far inland valleys, and 0-3SM where clouds intersect higher terrain, generally near the mountain slopes. Inland valleys will begin to see clearing after 16z Sun, with coastal locations scattering 18-20z. Some beaches/coastal areas may only see brief periods of scattering with clouds lingering through the afternoon. Clouds with similar bases will rebuild and fill back in after 00z Mon, once again filling the entire coastal basin.
Otherwise, mostly clear and VFR conditions through the period.
No hazardous marine conditions are expected through Thursday night.
Ca, None. PZ, None.
