Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
513 FXUS66 KSGX 291027 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 227 AM PST Sat Nov 29 2025 .SYNOPSIS... Cooler and dry this weekend. Patchy fog along the coast this morning, then increasing coverage tonight into Sunday morning. Weak Santa Ana winds develop Monday and weaken Tuesday for warmer and drier weather. There is a 20-35% chance of light precipitation Wednesday into Thursday, though confidence remains low. Another round of offshore winds will follow this system late in the week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Patchy low clouds and fog, which had pushed into the coastal mesas in the evening, have already drained back out towards the coast, especially in San Diego County. Where any fog remains over the coastal areas, visibility is down to one-quarter mile. Very weak offshore flow to the north may be enough to keep coverage patchy through the morning. Otherwise clear with light winds this morning. Weak upper level ridging off the coast will maintain high temperatures a few degrees above normal inland today. An upper level trough will drop out of the Pac NW and into the Great Basin late today into Sunday. This will bring cooling with highs returning closer to seasonal normals. Gusty west winds will also develop as onshore pressure gradients strengthen, with gusts around 35-45 mph in the wind prone passes and the desert slopes of the mountains. Gradients quickly turn offshore on Monday as high pressure settles into the Great Basin behind the trough. There will be modest upper level support in the form or northerly winds behind the digging trough (850 mb winds of 15-20 kt), albeit briefly. Winds are currently forecast to peak on Monday when gusts of 30-45 mph are likely below the passes and canyons and into the valleys, with isolated gusts around 50 mph near the Cajon Pass and Santa Ana Mountains. Otherwise warmer west of the mountains but cooler elsewhere on Monday. Offshore flow weakens and turns back onshore on Tuesday ahead of the next system for cooling and lighter winds. The upper level pattern is still questionable beyond Wednesday with the next trough dropping down from the north. Ensembles remain inconsistent with how far southwestward the trough digs, which impacts how much (if any) precipitation we`ll see. For Wednesday, around 58% of the ensemble members bring the low far enough west for at least light precipitation late the evening. By Thursday, 32% keep a weak positively tilted trough over the area (light precipitation), 25% have the track inside (dry), 22% develop a closed low off the coast (relatively heavier precipitation), and 21% have a weaker low closer to the Colorado River Valley (lighter precipitation at the coast but heavier inland). Even into Friday, 48% of the members keep a closed low somewhere in the vicinity of So Cal while the remaining 52% have a weaker open wave inland. With the closed low solution, we could continue to see cooler weather and light precipitation if the low is close enough, or with the more progressive/inside track it`ll be another round of Santa Ana winds and warmer and drier weather. For what it`s worth, the ECMWF AIFS ensemble, which has been performing fairly well, is much drier on Friday than its EPS and deterministic counterparts. For now just have the slight chance to chance (15-35%) PoPs limited to Wednesday morning through Thursday evening, then slightly warmer and dry weather Friday and Saturday. && .AVIATION... 290930Z....Coasts/Valleys...Patchy areas of low clouds based 300-700 ft MSL have been intermittent along coastal regions with VIS between 1/4 to 3 SM. Clouds have spread through the coast and inland 10-15 miles. Low clouds will begin to clear around 15-17Z for San Diego County and around 17Z for Orange County. Low clouds based 800-1200 ft MSL will redevelop and move ashore after 05Z Sunday and push further inland. .Mountains/Deserts...VFR conditions expected through the TAF period. && .MARINE... No hazardous marine conditions are expected through Thursday. && .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 AVIATION/MARINE...Villafane