200 FXUS66 KSGX 101634 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 934 AM PDT Tue Jun 10 2025 .SYNOPSIS... A high pressure ridge over the western states will bring warming for the coast and valleys followed by slow cooling of around 5 degrees for Wednesday through Friday. High pressure to the south will bring around 5 degrees of warming for the weekend followed by slow cooling for early next week. Night and morning coastal low clouds will continue to spread into portions of the valleys, then become patchier and less extensive for the weekend as the marine layer becomes shallower. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... This morning...The marine layer is about 2300 ft deep and low clouds had spread inland to the coastal slopes and also covered much of the IE. There was patchy light drizzle but no measurable amounts were reported as the saturated layer was thinner than the last several nights. The marine layer inversion is relatively strong and the low clouds are beginning to clear at the inland edges but low clouds could linger at the beaches into the afternoon. High pressure over the western states will continue to bring warm temperatures inland today. Temperatures in the inland valleys, mtns and deserts will be 3 to 11 degrees above seasonal averages. There is a 70-90 percent chance of exceeding 105 degrees in the lower deserts and about a 40 percent chance of exceeding 95 degrees in the Inland Empire. A semi-permanent low pressure system over the Gulf of Alaska with a series of shortwave troughs embedded in the flow over CA will weaken the high pressure and shift the ridge to the east and south. Along with a little stronger onshore flow, this could result in slight cooling for Wednesday through Friday. High temperatures on Friday will be mostly within a few degrees of average for the coast and valleys with the deserts around 5 degrees above average. High temperatures on Friday will range from around 70 near the coast to the 80s and lower 90s for the Inland Empire with 104 to 108 for the lower deserts. High resolution models indicate that the marine layer becomes a little shallower with low clouds and fog not spreading into the Inland Empire quite as much as it did this morning. The high pressure will reposition itself over AZ, NM and Sonora Mexico by Sat, with the ridge amplifying over the Inter-Mountain West. This will bring warming of around 5 degrees for the weekend, with Sunday high temperatures mostly 5 to 10 degrees above average. High temperatures on Sunday will range from the lower 70s near the coast to the 90s for the Inland Empire with 108 to 112 for the lower deserts. Monday will be a few degrees cooler. Current guidance indicates greater chances for patchier coverage of night and morning coastal low clouds for the weekend with coverage not extending inland much past the far western valleys as the marine layer becomes shallower. && .AVIATION... 101530Z....Coast/Valleys...Coastal low clouds based 900-1500 ft MSL with tops to 2300 ft MSL have started to retreat out of inland valleys. Scatter out continue through 17Z inland and 18-20Z at the coast, but very little if any clearing is expected along immediate coast. Low clouds to gradually move into western valleys after 02Z and overnight into Wednesday with similar timing, bases, vis reduced 1-5SM inland and over higher coastal terrain, and extent of coverage to this morning. Mountains/Deserts...Mostly clear skies and unrestricted vis today and tonight. && .MARINE... No hazardous marine conditions are expected today through Saturday. && .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...CSP