Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
181 FXUS66 KSGX 022030 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 130 PM PDT Sun Jun 2 2024 .SYNOPSIS... A weak trough over the West Coast will keep a deep marine layer in place through Monday. Pockets of early morning drizzle are likely in some coastal and valley areas late tonight through early Monday morning. High pressure building over the Great Basin Tuesday through Thursday will bring warmer weather to the valleys and mountains, and hot weather to the deserts midweek. Cooler next weekend with increasing onshore flow and a deeper marine layer. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Clearing of the marine layer clouds was much slower today than yesterday and most of Orange County, the Inland Empire and coastal San Diego County remained overcast at 1 PM. This lack of clearing was due to the deeper marine and thicker cloud deck today compared to yesterday. Tonight a Catalina Eddy strengthening over the coastal waters will keep the marine layer deep enough for clouds to fill the valleys tonight, and for areas drizzle west of the mountains late tonight through early Monday morning. From Tuesday through Thursday a 592 dm ridge builds over the eastern Great Basin. This ridge position will bring hotter days to the deserts where high desert highs Wednesday and Thursday will range from 97-103. Heat Risk values in this area meet the criteria for an Excessive Heat Watch which was issued today and will be in effect Wednesday and Thursday. Affected communities include Victorville, Hesperia, Apple Valley, Barstow and Yucca Valley. The Lower Deserts will also be hotter midweek with highs from 105- 110 at Palm Springs, Coachella and Thermal. Mountain areas will be warmer with highs from 80-90, as will the eastern portion of the Inland Empire with highs from 90-95. Warming in the coastal areas and the western valleys will be tempered by the marine layer and the cooling onshore sea breeze. Highs will range from the upper 60s at the coast to the upper 70s ten miles inland. Latest guidance suggests a slower breakdown of the ridge high pressure over the Great Basin later this week, and the desert heat may persist into Friday before being forced east by a deepening closed low over north-central Baja. This closed low, cut off from the jet stream, will slowly meander north-northeast across northern Baja Saturday, then cross into either Southern California or Arizona Saturday night and Sunday. This trough may generate isolated convection but that will depend on the instability and moisture parameters, and the ultimate track of the low. && .AVIATION... 022005Z...Coast/Valleys...BKN-OVC low clouds with bases 1500-2500 ft MSL with tops to 3000 ft MSL are slowly beginning to scatter out over the coastal basin. VIS restrictions on higher terrain where clouds and terrain intersect. Expect only a few hours of clearing at most today before low clouds redevelop across much of the same areas later this afternoon and evening. Much of the coast will likely see cloudy skies continue into tomorrow. Low clouds will gradually spread back inland after 02Z Mon, with similar bases. Mountains/Deserts...Clear skies with unrestricted VIS today. West winds gusting up to 40 kt will occur again 22Z Sun-10Z Mon from the mountain crests east through the desert slopes and into the deserts, including through/near San Gorgonio Pass. Gusts 25-30 kt near KPSP and KTRM. MOD UDDFS expected. && .MARINE... No hazardous marine conditions are expected through Thursday. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Excessive Heat Watch from Wednesday morning through Thursday evening for Apple and Lucerne Valleys. PZ...None. && $$ PUBLIC...Moede AVIATION/MARINE...Adams