147 FXUS66 KSGX 110427 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 927 PM PDT Tue Jun 10 2025 .SYNOPSIS... Slow cooling Wednesday through Friday, then 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... Evening update... It was a hot day inland with highs around 100-106 in the deserts. As suspected, gulf moisture into the low deserts suppressed high temperatures there though dew points were only in the mid 50s. Marine layer low clouds are quicker to spread inland this evening, already extending into parts of the western valleys. Elsewhere skies are clear outside of wildfire smoke near Apple Valley. No changes to the forecast this evening, though with southeast flow/gulf moisture continuing to spread into the lower deserts, temperatures will likely be on the lower end of the ensemble spread on Wednesday. Previous discussion... 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... 100300Z....Coast/Valleys...Coastal San Diego/Orange Counties have been overtaken by low clouds based 1000-1500 ft MSL. Expecting most valleys in San Diego/Orange Counties to fill in overnight, but should only reach western and southern portions of the Inland Empire. Bases lower some to 700-1200 ft MSL after 06z allowing for minor vis reductions (3-5 SM) for elevated inland areas. Low clouds clear from inland areas 16-18Z Wed, and coastal areas gradually clear 18-21Z, but linger along the immediate coast all day. Clouds slowly start to move inland again after 00z Thursday with similar to slightly lower bases. Mountains/Deserts...Mostly clear skies and unrestricted vis today and tonight. && .MARINE... No hazardous marine conditions are expected today through Sunday. && .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...KW AVIATION/MARINE...SS