758 FXUS66 KSGX 230421 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 921 PM PDT Sun Jun 22 2025 .SYNOPSIS... Minor day-to-day variations in temperatures through Tuesday. A gradual warming trend is expected for the middle to end of the week. The marine layer will bring night and morning low clouds to coastal areas through the week. Low clouds are expected to reach into the valleys at times, most likely during the first half of the week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... This evening...The marine layer remains about 2500 ft deep with a weak inversion but skies are clear except for a patch of low clouds off the coast of San Diego County. High-resolution models show about a 40-60 percent chance for low clouds in the coastal areas and western portions of the San Diego County valleys between about midnight and 10 am Monday. From previous discussion... A long wave troughing pattern will remain over the Western United States early this week. That will keep high temperatures 5 to 10 degrees below average through Tuesday. Marine layer low clouds and fog are expected each night and morning and will reach into the western portions of the valleys. On Wednesday the upper level troughing will shift east, but cyclonic flow aloft will remain over the region into Friday. Ensembles are in generally good agreement with upper level high pressure beginning to build in from the southeast into next weekend but there remains uncertainty in the placement of the ridge. Only about 25 percent of solutions have the ridge axis over the West Coast, which would result in the hottest conditions. Regardless, a gradual warming can be expected for the middle to end of the week with lingering uncertainty in just how hot it will get. Friday through Sunday, the difference between the coolest high temperature solution and the warmest is about 10 degrees for the valleys and mountains. NBM chances of the deserts reaching or exceeding 110 degrees is around 15 percent Saturday and closer to 30 percent Sunday. The building high pressure aloft should keep the marine layer shallower and more confined to coastal areas. && .AVIATION... 220300....Coast/Valleys/Coastal Mountain Slopes...VFR conditions throughout the region this evening. Low clouds with bases 1500-2500 ft MSL redevelop along the coastline 06-09z and spread into the valleys of San Diego/Orange Counties 09-12z. Clouds may briefly spill into the far western and far southern portions of the IE. Low clouds clear to the coast 15-17z Monday morning. 30% chance that BKN CIGs linger through the afternoon at the coast. Low clouds with similar bases begin to push inland again around 03-06z Tuesday. .Mountains/Deserts...Clear skies and largely unrestricted VIS through Monday evening. Wind gusts 25-35 kts Monday afternoon and evening with isolated gusts to 45 kts through mountain passes. && .MARINE... No hazardous marine conditions are expected through Thursday evening. && .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...PG AVIATION/MARINE...KW