FXUS66 KSGX 250955 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 255 AM PDT Sat Oct 25 2025 .SYNOPSIS... Cooler this weekend with breezy west winds on Sunday. Daytime temperatures will be a little below normal in the coastal areas and valleys, and a little above normal in the deserts. The marine layer will deepen, with stronger onshore flow driving low clouds and fog into the western valleys. High pressure and periods of offshore flow will bring warmer and drier weather with a shallower marine layer next week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... This morning...The marine layer is 1500-2000 ft deep and low clouds cover the coastal areas and portions of the inland valleys up to about 15 miles inland. Otherwise, skies will be mostly clear this morning. With a transient high pressure ridge overhead, the marine layer inversion is a little stronger which could slow down the clearing process today. The upper ridge over SoCal will be displaced to the east over the next 18-24 hours as a low pressure trough moves inland to the north. This will bring cooler conditions, stronger onshore flow and a deeper marine layer for today and Sunday as a pattern of high-zonal flow sets up aloft. High temperatures this weekend will be a few degrees below seasonal averages west of the mountains, but remain near or a little above average in the deserts. The stronger onshore flow will produce gusty westerly winds, mainly for the mountains and deserts. Winds will peak Sunday afternoon with gusts of 35 to 45 mph in the wind-prone locations of the mtns and deserts. As the the marine layer deepens, the onshore flow will push low clouds farther inland with fog on the higher inland terrain. At least through the middle of next week, the EC and GFS are in pretty good agreement with building a ridge of high pressure over the western US. The high pressure aloft and periods of weak offshore flow will bring warmer conditions through next week. Wednesday will likely be the warmest day before the ridge weakens later in the week in response to a minor shortwave trough moving inland to the north. High temperatures Wednesday will be up to 15 degrees above average for the inland valleys. High pressure aloft will also reduce the depth of the marine layer and restrict any low clouds/fog to the coastal areas during the nights and mornings. && .AVIATION... 251000Z...Coast and western Valleys...Low clouds based 700-1000 ft MSL currently over coasts and western valleys up to 15-20 miles inland. Clouds pushing into the western Inland Empire including KONT by 12Z. 30% chance low clouds reach KSBD. Vis reductions (1-5SM) are expected for elevated coastal terrain and inland valleys (i.e. KONT and maybe KCRQ). VIS improves and low clouds scatter 16-18z. Low clouds around 1000-1500 ft MSL will move in again starting 00-03Z Sunday with similar inland extent overnight. Inland Valleys/Mountains/Deserts...VFR conditions expected through the TAF period. SCT high clouds move in from the north Saturday afternoon. && .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...PG AVIATION/MARINE...KW