Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
833 FXUS66 KSGX 242044 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 144 PM PDT Fri May 24 2024 .SYNOPSIS... Cooling will continue through Saturday with gusty southwest to west winds in the mountains and deserts. The strongest gusts occur this afternoon and evening with the stronger gusts to 40 to 50 mph, locally 60 to 65 mph below the San Gorgonio Pass. Night and morning coastal low clouds will extend inland across all of the valleys and onto the lower coastal slopes of the mountains with slower daytime clearing for coastal areas. High pressure to the south will bring warming for Sunday through Thursday. The marine layer will become shallower with night and morning coastal low clouds only extending into western portions of the valleys by the middle of next week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... A deep marine layer remains evident on visible satellite imagery this afternoon, with clouds extending all the way over the Cajon Pass as of 1:30 PM PDT. The 12z Miramar sounding indicated a saturated layer from roughly 1800-2000 FT MSL to about 3000-3500 FT MSL. A strong inversion was also noted near the top of the saturated layer, roughly 9C strong. The deeper saturated layer and the strong inversion are the likely culprits for the very slow clearing process over much of Southern California, with low clouds just now beginning to scatter out over portions of the coastal mountain foothills. Short-term guidance suggests some slow clearing over the Inland Empire this afternoon, but most areas closer to the coast will likely see intermittent clearing, at best. This trend is expected to continue into Saturday with persistent onshore flow in place. There is a slight chance that the onshore flow leads to a reverse clearing event at the coast tomorrow, but confidence in this occurring is rather low at this time. Future soundings will help to assess the inversion strength and depth and lend more confidence to the degree of clearing tomorrow. The marine layer looks to deepen to around 4500 feet tonight, which will likely support patchy drizzle into tomorrow morning. The onshore flow is expected to be strongest today, with winds gusting 40 to 50 mph across much of the mountains and deserts this afternoon and evening. Higher gusts look to occur through and just below the San Gorgonio Pass, where gusts of 60 to 65 mph are expected. Sunday kicks off a warming trend for SoCal as upper level ridging builds in overhead. Highs will climb several degrees both on Sunday and Monday, followed by slower and more gradual warming through midweek. Most areas will still remain slightly cooler than normal through midweek, but the lower deserts will top out a few degrees warmer than seasonal normal starting Monday. This translates to highs of 99 to 105 degrees each day Monday through Thursday, with Wednesday and Thursday being the warmest days in the lower deserts. For most other locations, Wednesday and Thursday will be when temperatures rebound back to seasonal normals. The marine layer will also steadily decrease in depth during this time, though there will still be some degree of marine layer clouds each morning over the coasts and valleys. && .AVIATION... 242030Z...Coast/Valleys/Foothills...Lifting and Partial clearing of the marine layer clouds will continue across inland areas this afternoon. With less clearing expected along the coast. Low clouds will begin to spread back inland starting 02Z Sat with BKN-OVC basses 1800-2500 FT MSL extend through the foothills Saturday morning. Locally reduced vis where low clouds and terrain intersect. Mountains/Deserts...FEW-SCT AOA 25,000 FT MSL through Fri night. W- SW wind gusts of 25-40 knots over/east of mtns after 21z Fri, strongest after 00z Sat. Locally reduced vis of 3-5 SM in local BLDU. && .MARINE... Northwest winds near 20 knots will occur in the outer coastal waters each afternoon and evening through Sunday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Wind Advisory until 2 AM PDT Saturday for San Gorgonio Pass Near Banning. PZ...None. && $$ PUBLIC...Adams AVIATION/MARINE...Suk