The marine layer will deepen overnight into Wednesday morning before becoming shallower again for Thursday into early next week. Areas of drizzle or light rain near the coast are possible tonight into Wednesday, with no impacts expected. Wednesday will be a few degrees cooler than today, before warmer conditions Thursday into early next week. The pressure gradient will rapidly switch from onshore to offshore for the middle to end of the week with periods of gusty Santa Ana winds.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Visible satellite at 9 AM was showing mostly clear skies across the area, the only exception was a patch of fog over northern Orange County and low clouds over the coastal waters. The marine layer is expected to rapidly deepen as a low pressure system moves south into the Great Basin tonight. By Wednesday morning, the marine layer is expected to be about 4500 ft deep with low clouds reaching the coastal slopes of the mountains. There could be some light showers or patchy drizzle late tonight into early Wednesday morning for the inner coastal waters into adjacent coastal areas with the chance of measurable rainfall less than 10 percent.
As the upper level low digs into the Great Basin a 1030 mb surface low will develop. This will bring periods of gusty offshore winds to foothills and coastal mountain slopes; warming conditions; and mostly clear skies across the area. Gusty north winds will develop through and below the Cajon Pass on Wednesday afternoon with more widespread and stronger northeasterly winds for Wednesday night along and below the coastal slopes of the mountains with the stronger gusts to around 45 mph. Northeast to east winds will continue for Thursday into Friday morning, but with decreasing coverage and strength. Gusts on Friday are expected peak around 35 mph. Lowest daytime humidity on Thursday for the valleys and inland coastal areas will fall to 15 to 20 percent and 20 to 25 percent Friday afternoon.
Highs today are expected to be near normal for this time of year, with some locations a little warmer than normal and others a little cooler. Few degrees of cooling is expected into Wednesday, with highs a few degrees below average. A gradual warming will occur Thursday, with further warming expected through the weekend into early next week. By Tuesday, highs will be 10 to 15 degrees above average for inland areas.
021700z. Coasts/Valleys, A stubborn patch of FG in the vcty KSNA will clear out within the next hour. Otherwise, SKC through the afternoon. Low clouds based 600-1200 ft MSL return to San Diego County 00-03Z Wed. Bases will rise steadily overnight to 2000-2500 ft MSL as coverage expands to include the entire coastal basin. Patchy -DZ expected, especially near the coastline from 10-16Z. Clouds scatter out 15-18Z.
Mountains/Deserts, VFR conditions through the period with FEW-SCT high clouds AOA 20 kft after 21Z. Westerly winds gusting 25-35 kts through mountain passes and along east-facing slopes after 03Z Wed.
No hazardous marine conditions are expected today through Saturday.
Astronomical high tides are forecast to occur each morning Wednesday through Friday, threatening minor tidal overflow and beach erosion. Chances of these impacts are higher Wednesday and Thursday mornings as elevated surf up to 4-6 feet combines with the high tides, especially in San Diego County. Check the Coastal Hazard Message for details.
Ca, Beach Hazards Statement from this evening through Friday morning for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, None.
