Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
372 FXUS66 KSGX 130350 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 850 PM PDT Mon Aug 12 2024 .SYNOPSIS... Dry and seasonal weather will prevail through the weekend. Breezy westerly winds are expected through parts of the mountains and deserts through Tuesday night. The marine layer will provide more low clouds and fog to coastal areas each night and morning. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Satellite imagery at 9 PM was showing patchy low clouds developing locally at beaches. Low cloud coverage is expected to be more widespread than last night. High temperatures Tuesday are expected to be the same to a degree or two warmer than today, but most locations will have seasonal temperatures for this time of year. A few gusts to 40 mph occurred earlier today near the San Gorgonio Pass, with a local gust to 50 mph at Whitewater. From previous discussion issued 2 PM August 12, 2024... An upper level trough of low pressure off the Pacific Northwest coast has broken down our hot ridge of the weekend. The trough will continue to clear out our area of any remaining monsoonal moisture. Additionally, the trough will boost onshore winds during the afternoons and nights today through Tuesday night. Strongest winds will blow through mountain passes into adjacent deserts, where top gusts could reach 40 mph. With no more monsoon disruption, the marine layer will rebound so that coastal low clouds and fog will become more uniform, extensive and longer lasting. But the marine layer doesn`t appear to deepen enough for clouds/fog to extend beyond the westernmost valleys each night and morning. A coastal eddy could enhance the marine layer and cloud coverage Wednesday and Thursday. Counterintuitively, high pressure aloft actually strengthens those days, so inland temperatures will be a few degrees higher. Monsoon moisture appears to increase this coming weekend, leading to a very small but increasing chance of thunderstorms for mountains and deserts Sunday and Monday. Latest guidance continues to show this trend, but it`s still not enough to make our forecast yet through Monday. Something to watch and fine tune in coming days. The low pressure to our northwest and a growing high pressure to our east seem to set up a stationary battleground with SoCal right in between the two. Some guidance indicates the trough dominating while other guidance suggests the ridge taking precedence. We have a modest warming trend in our forecast for early next week. && .AVIATION... 130320Z...Coast/Valleys...Patchy low clouds returning to the coastal areas at this hour with bases 900-1200 ft MSL and tops to about 1400 ft MSL. Low clouds could spread 10-15 miles inland by 15Z. Chances for CIG impacts at coastal TAF sites around 45 percent at 10Z, increasing to around 80 percent by 14Z at KSAN and to around 60 percent at KCRQ and KSNA. Local VIS 3-5 miles on higher coastal terrain. Expect clearing to the beaches 16Z-18Z. Mountains/Deserts...Mostly clear with unrestricted VIS through Tuesday morning. && .MARINE... No hazardous marine conditions are expected through Thursday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ PUBLIC...CO/MM AVIATION/MARINE...PG