Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
962 FXUS66 KSGX 211246 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 546 AM PDT Tue May 21 2024 .SYNOPSIS... Through Wednesday, slowly warmer with the deserts warming to a few degrees above average and the coast and valleys remaining below average. Cooling for Thursday through Saturday with slower and more limited daytime clearing for the coast into the valleys as the marine layer deepens. There will also be stronger and gusty southwest to west winds for the mountains and deserts. High pressure to the south will bring a warming trend for Sunday into the middle of next week with the marine layer becoming gradually shallower. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .SHORT TERM (Today through Thursday)... Low pressure across the area will slowly weaken through Wednesday. The marine layer is near 4000 feet deep early this morning. While the coastal low clouds extend well inland and onto the lower coastal mountain slopes, cloud bases are also high with satellite imagery showing some coverage gaps in the clouds for portions of the coast and valleys. There will brief northerly lower level flow for this morning and early afternoon with clearing of the low clouds for the Inland Empire slightly earlier than on Monday. The marine layer will be a little shallower for tonight into Wednesday morning, around 3000 feet deep, with night and morning coastal low clouds extending well inland across most of the valleys. Today and Wednesday will be a little warmer with the greatest warming today for the mountains and inland valleys. With the warming, Wednesday high temperatures will be a few degrees above average for the deserts while remaining below average for the coast and valleys. A trough of low pressure moving southward off the West Coast will move inland through southern California around Friday night. This will bring stronger onshore flow with a more persistent coastal eddy developing on Thursday and continuing into Friday. The marine layer will deepen to 4500 to 5000 feet for Friday into Saturday. High temperatures on Thursday will be a few degrees cooler. There will be gusty southwest to west winds for the mountains and deserts with the stronger gusts to 40 to 50 mph. && .LONG TERM (Friday through Memorial Day)... The marine layer will deepen into Friday and Saturday with night and morning coastal low clouds extending inland across all of the valleys and onto the coastal mountain slopes. Daytime clearing for the coast into the valleys will be limited and slow. The cooling trend will continue into Saturday with Saturday high temperatures 5 to 10 degrees below average for lower elevations to 10 to 15 degrees below average for the mountains and valleys with Saturday high temperatures in the lower to mid 60s near the coast and mostly in the 80s for the lower deserts. High pressure to the south will bring a warming trend for Sunday into the middle of next week. The marine will gradually decrease in depth, but with night and morning coastal low clouds still extending inland into portions of the inland valleys for the middle of next week. Monday high temperatures will warm to a few degrees above average for the deserts with coast and valleys still a few to around 5 degrees average, mostly in the mid 60s near the coast and in the 90s in the lower deserts. && .AVIATION... 210930Z...Coast/Valleys/Foothills...Low clouds with varying bases of 1800-3500 feet MSL and tops to 4200 feet will continue this morning. Foothill terrain locally obscured in clouds/fog. Clearing will occur in most areas 15-19Z, but with partial or intermittent clearing at the coast. Low clouds will push inland after 02Z and fill the coastal basin overnight into Wednesday. Bases would be 1500-2000 feet MSL with more vis restrictions far inland. Mountains/Deserts...Areas of westerly winds with gusts 25-40 kt will continue through 15Z along through mountain passes and into the deserts, along with MOD UDDFS and LLWS. Clear skies with unrestricted VIS will continue today and tonight. && .MARINE... No hazardous marine conditions are expected through Saturday. && .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...17 AVIATION/MARINE...MM