Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
516 FXUS66 KSGX 051535 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 835 AM PDT Fri Sep 5 2025 .SYNOPSIS... Generally seasonal temperatures will prevail through the weekend with decreasing chances for afternoon thunderstorms for the mountains and deserts on Saturday with dry weather for Sunday. A low pressure system will move slowly inland into the western states next week bringing drying and a gradual cooling trend. With the cooling, high temperatures on Wednesday and Thursday will be a few degrees below average near the coast to as much as 10 to 15 degrees below average for the mountains, high desert, and inland valleys. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .Morning Update... GOES imagery this morning shows low clouds around ten miles inland from the coast, where some valleys are beginning to clear. Outflow from a complex of thunderstorms in Arizona has also contributed to some clouds out in the lower deserts as well. No major forecast changes for this afternoon as thunderstorms will begin to arise across the mountains. Thunderstorms will reform again once more on Saturday. High temperatures will be similar through the weekend before quieter and cooler weather moves into the region by next week. .Previous Discussion (356 AM Friday)... .SHORT TERM (Today through Sunday)... Late Thursday evening, outflow from thunderstorms spread westward into the deserts and mountains in San Diego County and northwestward across the Coachella with the strongest gust to 46 mph at Thermal at 10:32 PM. This outflow pushed dewpoints in the lower deserts mostly into the lower 70s. Coverage and intensity of thunderstorms for this afternoon for the mountains and deserts is expected to be similar to Thursday afternoon with the greatest coverage and rainfall amounts over the mountains of San Diego and Riverside Counties with the highest HREF 90th percentile hourly rainfall of around 0.9 inch for this afternoon and around 0.5 inch for Saturday afternoon with lesser coverage and amounts. Dry weather is expected for Sunday. Coverage of night and morning coastal low clouds will gradually increase through the weekend with low clouds over the coastal waters spread locally inland into coastal areas late each night. High temperatures for today may be a few degrees cooler than Thursday followed by a degree or so of warming on Saturday and another degree or so of warming on Sunday. High temperatures on Sunday are expected to be near average at the coast to a few degrees below average for inland areas, ranging from the 70s near the coast to the 90s for the Inland Empire with 100 to 104 for the lower deserts. && .LONG TERM (Monday through Thursday)... A low pressure system will move slowly inland into the western states next week bringing drying a gradual cooling trend. With the cooling, high temperatures on Wednesday and Thursday will be a few degrees below average near the coast to as much as 10 to 15 degrees below average for the mountains, high desert, and inland valleys. High temperatures on Wednesday and Thursday will range from the lower to mid 70s near the coast to the upper 70s to mid 80s for the Inland Empire with the lower to mid 90s for the lower deserts. Night and morning coastal low clouds and fog will spread into the far western valleys late each night at times. && .AVIATION... 051530Z...Coast...Low clouds based 500-1200 ft MSL have filled into most coastal areas and some western valleys this morning, with only slight erosion occurring from east to west at this hour. There are also several locations with reduced vis down to 2SM in BR. This is expected to clear with improving visibilities to the beaches by 15- 17Z, and clear over waters shortly, thereafter. Clouds return to waters and coastal land areas later this evening after 06z Saturday with similar bases, but less inland extent. Valleys/Mountains/Deserts...Isolated SHRA/TSRA expected over San Diego County and southern Riverside County mountains again this afternoon from 19-01Z, with slighter chances (15-20%) for more northerly mtns and deserts/desert foothills. CB bases of about 10000 feet MSL with TSRA tops to 35k feet. Gusty, erratic winds, blowing dust with low visibility, lightning, and lower bases 6000-9000 feet MSL will occur with any TSRA. && .MARINE... No hazardous marine conditions are expected through Monday. && .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...APR AVIATION/MARINE...Stewey