323 FXUS66 KSGX 191653 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 953 AM PDT Thu Jun 19 2025 .SYNOPSIS... Low pressure moving inland into the western states will bring cooling through Saturday with Saturday high temperatures as much as 8 to 12 degrees below average for the mountains, inland valleys, and high desert. There will gusty southwest to west winds during the afternoons and evenings for the mountains and deserts with the stronger gusts to 35 to 45 mph. The marine layer will deepen with night and morning coastal low clouds spreading farther inland to the valleys. For Sunday through Wednesday, low pressure will weaken some, but remain across the area. High temperatures will warm 5 to locally 10 degrees but remain below average by around 5 degrees. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .Morning Update... Low clouds are quickly scattering to the coast this morning. Expecting clouds to clear at the coast and nearshore waters again given that the marine layer inversion continues to slowly weaken. Temperatures today cooler than yesterday with moderate HeatRisk becoming confined to just the low deserts. Models still indicate a cooling trend through the weekend with increasing westerly winds for the deserts/desert slopes as an upper trough pushes into the PNW. .Previous Discussion (244 AM PDT)... .SHORT TERM (Today through Saturday)... The marine layer has deepened to around 2000 feet with satellite imagery showing coastal low clouds covering all of the Orange County coastal plain and the western half of the San Diego County valleys. Through sunrise, the low clouds may begin to spread into far southern and far western portions of the Inland Empire. Wednesday high temperatures were a few degrees cooler than Tuesday for the coast and valleys. A low pressure system moving inland into the western states will spread cooling inland through Saturday. Saturday high temperatures will be as much as 8 to 12 degrees below average for the mountains, inland valleys, and high desert with high temperatures ranging from around 70 near the coast to the mid 70s to lower 80s for the Inland Empire with around 100 for the lower deserts. The marine layer will deepen to around 2500 feet for Saturday with night and morning coastal low clouds spreading farther into the valleys. Stronger onshore flow will also bring stronger and gusty southwest to west winds for the deserts onto the desert slopes of the mountains with the stronger gusts during the afternoons and evenings to 35 to 45 mph. && .LONG TERM (Sunday through Wednesday)... Low pressure will weaken some, but remain across the area. High temperatures will warm 5 to locally 10 degrees but remain below average by around 5 degrees. The marine layer will decrease in depth to around 1500 to 2000 feet with night and morning coastal low clouds spreading inland into the western valleys. && .AVIATION... 191530Z....Coast/Valleys...Low clouds based at around 800-1400 feet MSL and tops to 2000 feet will continue to scatter out by 18Z. Low clouds to develop after 01Z and push inland overnight into most of the inland valleys by 13Z Friday. Bases should be closer to 1200-1500 feet MSL, with vis 3-5SM inland. .Mountains/Deserts...Clear skies and unrestricted VIS through Friday morning. Westerly winds increase after 22Z with gusts 25-40 knots through mountain passes locally into deserts, producing pockets of up/downdrafts in lee of ridges. && .MARINE... Northwest winds may gust close to 20 knots near San Clemente Island Friday afternoon and evening. Otherwise, no hazardous marine conditions are expected through Monday. 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. && $$ UPDATE...KW PUBLIC...17 AVIATION/MARINE...MM