683 FXUS66 KSGX 121250 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 550 AM PDT Tue May 12 2026 .SYNOPSIS... Through Wednesday, a weak low pressure system moving into southern California will deepen the marine layer to around 3000 feet with night and morning coastal low clouds spreading farther into the valleys and with slower afternoon clearing for San Diego County coastal areas. It will be slightly warmer for Thursday and Friday with the marine layer decreasing in depth, then slightly cooler for the weekend. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .SHORT TERM (Today through Thursday)... A weak low pressure system will move toward the southern California coast today and move inland through southern California on Wednesday. The marine layer became shallower on Monday, decreasing in depth to around 1500 feet. Satellite imagery after midnight shows widespread low clouds over the coastal waters spreading into the western half of the valleys in San Diego County and spreading northward and inland across the Orange County coastal plain. The marine layer is expected to be begin deepening before sunrise with deepening to around 3000 feet for late tonight into Wednesday morning. The coastal low clouds are expected to spread into portions of the inland valleys early this morning, then inland across most of the coast and valleys for tonight into Wednesday morning. High temperatures for today will cool as much as 15 to 20 degrees for portions of the inland valleys and as much as another 8 to 12 degrees on Wednesday for the mountains and high desert. High temperatures on Wednesday will be a few to around 5 degrees below average for the coast and valleys and around 5 degrees above average for the lower deserts. High temperatures on Wednesday will range from the mid to upper 60s near the coast to the mid 70s to lower 80s for the Inland Empire with the lower deserts in the upper 90s to 103. High temperatures on Thursday will be a few degrees warmer with the marine layer beginning to decrease in depth. && .LONG TERM (Friday through Monday)... High temperatures for the mountains and deserts will warm another few degrees on Friday. High temperatures on Friday will be as much as 10 degrees above average for the deserts, reaching 102 to 106 for the lower deserts. High temperatures for inland areas will cool a few degrees on Saturday and another few degrees on Sunday with Sunday high temperatures a few to around 5 degrees above average for most areas. High temperatures on Sunday will range from around 70 near the coast to the upper 70s to mid 80s for the Inland Empire with the lower deserts in the mid 90s to around 100. High temperatures on Monday will warm a few to around 5 degrees. && 120930Z...Coast/Valleys...Low clouds based 600-900 feet MSL and tops to 1600 feet will continue over coastal areas and spread locally into inland valleys this morning. Vis reduced 0-5SM mainly along higher coastal and valley terrain. Scatter out not really expected near the coast, but 17-20Z inland. Where cigs persist, they will lift during the day to 1500-2500 feet MSL. These lifted low clouds will spread inland after 01Z, and rapidly fill the entire coastal basin to the foothills overnight into Wednesday. Vis reduced 0-5SM over higher valley terrain and foothills and in patchy -DZ. Otherwise...SCT high clouds and VFR conditions today and tonight. && .MARINE... No hazardous marine conditions are expected 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...17 AVIATION/MARINE...MM
NWS SGX Office Area Forecast Discussion