FXUS66 KSGX 040514 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 914 PM PST Tue Dec 3 2024 .SYNOPSIS... Cooler Wednesday as an upper level low moves over. Low clouds are expected to reach into portions of the valleys tonight into Wednesday morning. The marine layer will become shallower for Thursday and Friday. Warmer and drier conditions with weak to locally moderate northeasterly winds Friday and Saturday. Dry conditions will continue into early next week, with the potential for additional rounds of Santa Ana winds. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Evening update... Low clouds have returned to the coastal areas this evening and have already begun to spread into portions of the western valleys in San Diego County. The 00Z KNKX sounding shows the base of the marine inversion has risen to around 1900 ft MSL, deep enough that any fog will be very localized tonight. Otherwise mostly clear skies and light winds overnight. Previous discussion... The marine layer will start to become shallower Wednesday night into Thursday with the return of weak offshore flow, keeping areas of low clouds and fog mostly confined to coastal areas. Areas of low clouds are expected again Thursday into very early Friday before breezy northeast winds develop. Highs on Wednesday are expected to be a few degrees cooler than today. Even with the slight cooling, temperatures away from the coast will remain above average. Warming is expected for Thursday through Saturday. High pressure will build aloft just off the US West Coast for Friday and Saturday with an area of low pressure aloft over Arizona and northern Mexico. Weak to locally moderate northeast winds are expected, along with warm and dry conditions. High temperatures Friday and Saturday will be 7 to 15 degrees above average. Peak wind gusts will likely be 35 to 45 mph on the coastal slopes of the mountains, mountain foothills, and locally into the eastern valleys. Early next week, an area of low pressure will dig south into northern United States, with a ridge of high pressure near the US West Coast. There is still a lot of uncertainty on where the low will end up. For Monday, about 50 percent of solutions have the low digging into the Great Basin, with 50 percent showing the low's position further east and digging into the Upper Midwest. The uncertainty continues for Tuesday, with about 55 percent of ensemble solutions showing the low digging into the Four Corners region with the other 45 percent showing the low further east over the Midwest. The ultimate placement of this low will determine how strong any Santa Ana winds that develop would be. The overall pattern will also have an impact on temperatures for early next week. If the ridge axis is centered more over the US West Coast, the forecast will trend warmer with cooler solutions more likely if the low digs south into the Great Basin/Four Corners and the ridge axis stays just offshore. Current forecast follows the NBM for early next week. Dry conditions look likely to prevail into early next week. && .AVIATION... 040415Z....Coasts/Valleys...Satellite shows low clouds and fog building along the coast which will push up to 15 miles inland overnight. Bases generally around 800-1200ft MSL with some slight lowering at times between 10z-15z. VIS may fall to 4-6SM along the coast, locally lower at times, with VIS down to 0-3SM for western valley areas and coastal terrain. Clearing/lifting should begin around 18z-19z Wednesday, although low stratus will linger along the beaches beyond this period. Low clouds build inland again Wednesday night, continuing into Thursday morning. Mountains/Deserts...FEW-SCT high clouds at or above 15,000 feet MSL through tonight, clearing by Wednesday morning. Otherwise, mostly clear skies and VFR conditions prevail through Wednesday afternoon. && .MARINE... No hazardous marine weather conditions are expected 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...SS/CO AVIATION/MARINE...Zuber