Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
045 FXUS66 KSGX 122045 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 145 PM PDT Mon Aug 12 2024 .SYNOPSIS... With the departure of monsoonal moisture today, 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... We`re just not feeling the thunderstorm chances this afternoon. The monsoonal moisture appears to be leaving faster than the convective forces can work with it to produce any thunderstorms. Patchy low clouds and fog currently along the coast will get more organized this evening. An upper level trough of low pressure off the Pacific Northwest coast has broken down our hot ridge of the weekend. Temperatures inland are a few degrees lower than at this time yesterday, so back to seasonal normals. 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... 122100Z...Coast/Valleys... SCT high clouds with bases to 15000ft- 20000ft MSL possible through the afternoon. Redevelopment of patchy low clouds at coastal sites expected again tonight as early as 06z, with bases to 1000ft MSL and localized VIS reductions down to 3-5SM for higher coastal terrain and valleys. Mountains/Deserts...Unrestricted VIS with FEW-SCT to 20000ft MSL through the evening. FEW Cu with bases to 12000ft MSL near the mountains this afternoon with iso TSRA (10%-15% chance) which may bring gusty and erratic winds. Mod up/downdrafts near the mountains this afternoon. Impacts from storms not expected at any TAF sites, and storms diminish by sunset. && .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...MM AVIATION/MARINE...Suk