Monsoonal moisture in place brings a slight chance for showers and thunderstorms for the desert slopes this afternoon. Above average high temperatures today will cool to below average for Thursday through the weekend, then warm to above average by the middle of next week. Night and morning coastal low clouds will spread farther into the valleys by the weekend.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
With fairly neutral flow aloft, the anomalous mid-level moisture that has been in place the last several days remains in place across the region. The taller mountain peaks along the Baja spine have already kicked off a few thunderstorms today with some cumulus on the mountain peaks in our area in response to the ample moisture. Similarly to yesterday, some high-res models spawn a few showers/t- storms over the mountains in the mid afternoon. However, should any develop, any showers/storms will likely be short lived as a strong dry air layer atop the mid level moisture serves to choke any updrafts out. A brief downpour and some stray lightning strikes do remain possible during the brief window of a storm's life though.
This mid level moisture is also contributing to the mild conditions many of the inland areas have been experiencing the last several days in two ways. First is the inhibition of radiational cooling at night, which is also serving to disrupt the marine layer some and keep it more confined to the coast than what is normally seen this time of year. Afternoon highs are running about 5-10 degrees above average today with overnight lows about 5-10 degrees above average for the inland areas and especially the deserts.
Westerly winds increase in the low to mid levels Wednesday morning, kicking out the monsoonal moisture, eliminating the precipitation chances, and moderating the temperatures back to seasonal norms. Relatively neutral flow aloft through mid week keeps the weather quiet with near normal temperatures. A weak but broad upper trough approaching the west coast on Thursday helps to deepen the marine layer and bolster the cooling trend some, with afternoon highs running 5-10 degrees below normal into the weekend. Clusters then favor ridging to build back in early next week, bringing warmer temperatures and squishing the marine layer back down some.
161730z, Coast/Valleys, Patchy low clouds based 1200-1500 feet MSL will persist along the immediate coast this afternoon. These clouds will push ashore after 03Z and March into some inland valleys overnight. Bases should lift to 1500-1800 feet MSL. Vis reduced to 3-5SM in valleys. Scatter out Wednesday 16-18Z.
Mountains/Deserts, SCT to locally BKN cumulus clouds 10000-15000 feet MSL with isolated -SHRA over mountains and desert near Mexico border 20-01Z. Clear after 03Z. Breezy westerly winds gusting 25-35 kts through mountain passes and into deserts 19-06Z.
No hazardous marine conditions are expected through Saturday.
Elevated surf and strong rip currents continue through Friday. Surf of 3-5 feet with sets to 6 feet are expected at south-facing beaches. Surf for southern San Diego County will be slightly lower, but hazardous swimming conditions with high rip current and longshore current risk will still exist. See the Beach Hazards Statement for more details.
Ca, Beach Hazards Statement through Friday evening for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, None.
