High temperatures near normal Thursday with southwest to west winds for the mountains and deserts gusting to 35 to 45 mph. Winds turn offshore on Friday with northeast winds along and below the coastal slopes of the mountains gusting to 35 to 45 mph. Warmer with weaker winds for the weekend with high temperatures warming to around 5 to 10 degrees above average. Cooler and breezy early next week as a low pressure system moves toward the California coast, but there remains a large amount of uncertainty in how this system progresses.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Evening update, Low clouds are beginning to redevelop over the coastal areas this evening, becoming more widespread and moving into the western valleys late tonight. Otherwise increasing high clouds across the region into Thursday ahead of an upper level trough approaching the West Coast. This trough will result in some cooling on Thursday with high temperatures near normal.
Previous discussion, Of most highlight from this trough late week will be the wind, with strengthening onshore flow on Thursday, followed by offshore winds late Thursday into Saturday. The elevated onshore flow Thursday afternoon will be felt most in the mountains/passes, adjacent deserts, and the high deserts. Wind gusts 35-45 mph expected in these areas, with localized areas up to 55 mph in the mounains and vulnerable mountain passes. With gusts upwards of 40-45 mph in the High Deserts, a Wind Advisory remains in effect from 11 AM Thursday through 2 AM Friday. As the upper trough pushes southeastward and surface high pressure spills into the Great Basin, winds will quickly switch to offshore, forcing north to northeasterly wind gusts of 35-45 mph in and below mountain passes, locally up to 55 mph within passes. Timing of the flip to offshore looks to be overnight Thursday into Friday morning, with the peak gusts late Thursday morning to around noon. Gusts look to wane by the afternoon hours, with another weak push of easterly offshore winds Saturday. The offshore winds bring in warmer and drier air to the inland valleys, with high temperatures 5-10 degrees above normal by Friday, continuing into Saturday.
The forecast becomes much more uncertain early next week as global ensembles continue to struggle with the resolution of a large upper trough set to near the California coast Monday into Tuesday. Regardless of the track of this low, temperatures will remain on the cool side to start next week with elevated onshore winds likely. Depending on the track of this storm, some light precipitation may be brought to southern California, but details will have to continue to be refined in the coming days.
160445z, Coasts, Low clouds are beginning to form along the San Diego coast around 1000-1500ft MSL. Low clouds will increase in coverage but are expected to be intermittent SCT/BKN cigs. Low clouds will scatter out 16-17Z.
Mountains/Deserts, Strong southwest to west winds are expected after 18Z with gusts up to 30 to 40 knots possible. Winds are expected to shift to offshore after 06Z Friday but will remain just as gusty, spreading along and below the coastal slopes of the mountains.
Otherwise, BKN/SCT high clouds AOA 20000ft MSL and VFR conditions expected through the TAF period.
Wind gusts to reach around 20 kts near San Clemente Island Thursday afternoon and evening. Otherwise, no hazardous marine conditions are expected through Sunday.
Ca, Wind Advisory from 11 AM Thursday to 2 AM PDT Friday for Apple and Lucerne Valleys.
PZ, None.
