FXUS66 KSGX 240417 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 917 PM PDT Thu Oct 23 2025 .SYNOPSIS... Fair weather will continue across the region into next week. Warmer Friday followed by cooling through the weekend. High pressure and periods of weak offshore flow will bring warmer and drier weather with a shallower marine layer Monday through Wednesday. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Evening update... Skies are clear this evening with any low clouds generally along and west of San Clemente and Catalina Islands. Surface pressure gradients are trending more offshore to Tonopah, but remain weakly onshore to the local deserts. Any weak offshore flow tonight will not be enough to keep marine layer stratus out, especially as a coastal eddy is forecast to develop. The 00Z KNKX sounding shows the marine inversion has lowered to around 1200 ft MSL, limiting low clouds to the coastal areas and coastal mesas/far western valleys late tonight into Friday morning. With the upper level ridge moving overhead, the marine layer could become even more shallow, potentially resulting in fog over the coastal mesas. The ridge moves overhead during the day Friday, bringing warming across the region with highs around 5-8 degrees above normal. Previous discussion... High pressure will weaken by this weekend, as large trough moves into the West Coast. This will bring cooler weather to the region with highs becoming closer to normal readings for late October. The tightening pressure gradient will allow for increased westerly winds over the region, mainly across the mountains and deserts. NBM probabilities show near a 50% chance in seeing wind gusts over 35 MPH across the high desert by Sunday afternoon/evening. E-W passes may gust near 50 MPH at times as well. Model guidance continues to be in good agreement next week, depicting high pressure strengthening over Mexico and the Desert Southwest by Monday. This will start a warming trend across Southern California as the high gains strength into the week. By Tuesday and Wednesday, temperatures will rise around 5-10 degrees above seasonal normals as weak to moderate offshore flow develops. High temperatures have the potential to reach 90 degrees across the Inland Empire and western valleys by this time period. Models continue to diverge slightly on where exactly the high becomes placed by later next week, but the ridge looks to slowly weaken during this time, leading to a subtle decrease in high temps. && .AVIATION... 240310Z...Coast/Valleys...Low clouds well offshore will gradually move ashore in areas after 06Z, with more widespread impacts not expected until after 10Z. Bases initially around 900-1200 ft MSL could lower slightly overnight to 700-1000 ft MSL. 70% chance for CIGs at KSAN/KCRQ by 12Z, 40% chance at KSNA overnight. Low clouds majority clearing 15-17Z, then redevelop and move back ashore after 25/02Z with similar bases around 700-1000 ft MSL. Mountains/Deserts...VFR and clear skies through the TAF period. && .MARINE... No hazardous marine conditions are expected through Tuesday. && .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/APR AVIATION/MARINE...CSP