Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
374 FXUS66 KSGX 060816 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 116 AM PDT Sun Apr 6 2025 .SYNOPSIS... Warm weather will prevail through the week. Areas of low clouds and fog may return to the coastal areas by Monday morning. Inland highs will be 10 to locally 20 degrees above normal Wednesday through Friday. Cooler next weekend, though it is uncertain how much cooling will occur. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Skies are clear this morning with mostly light winds as surface pressure gradients have turned weakly onshore to the local deserts. The broad upper level trough will continue to progress eastward today, allowing the upper level ridge to shift overhead. This will bring another 5-8 degrees of warming inland, though coastal areas will see little change or even some cooling with a return of onshore flow. The upper ridge shifts inland and flattens on Monday as another trough pushes eastward through the Pac NW, resulting in a few degrees of cooling west of the mountains but minor warming in the deserts. The marine layer begins to rebuild late tonight with a 50-60% chance of low clouds and fog along the coast by Monday morning. High pressure begins to build in from the south and the upper jet shifts slightly northward on Tuesday for another degree or two of warming across the region. This ridge amplifies across the western US into Thursday, bringing more significant warming. By Wednesday, highs will be around 10-15 degrees above normal inland, and around 5 degrees above normal near the coast. Thursday is expected to be the hottest day with highs peaking at 15-20 degrees above normal away from the coast. The NBM has a 70-90% chance of highs of 90 degrees or more in the Inland Empire and high desert on Thursday, and a 60-80% of highs of 100 degrees or more in the Coachella Valley and around Borrego Springs/Ocotillo Wells on Thursday. Otherwise areas of low clouds and fog, potentially dense, will continue near the coast during the nights and mornings through at least Wednesday. Ensemble spread remains with the progression of the trough off the West Coast into the weekend. The slower solutions (around 20% of the members) have the ridge barely budging on Friday, maintaining the warmer weather, with the most extreme members continuing the warming trend on Friday. Ensemble means and deterministic NBM offer only minor cooling. The spread increases through the weekend, though the overall trend is for cooler weather and stronger onshore flow. && .AVIATION... 060800Z...Currently, VFR conditions dominate the region. There is less than a 5% chance of CIGs expected through the early morning hours, mainly right along the immediate coastal areas of southern San Diego County if this develops. There could also be some areas of BCFG or MIFG for portions of the inland valleys. Typical diurnal afternoon westerly flow returns today. The marine layer looks to have a much higher probability of returning tomorrow night and filling in after 06z, with generally about a 60 to 90% chance of CIGs of 500-1000ft MSL right along the coastal areas of Orange and San Diego Counties, and about a 20 to 60% chance of CIGs of about 1000-2000ft MSL extending to around 10-15 SM inland. Scattering out of this marine layer should occur beginning around 15z on Monday. && .MARINE... No hazardous marine conditions are expected through Friday. && .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...SS AVIATION/MARINE...Stewey