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Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
259 FXUS66 KSGX 122052 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 152 PM PDT Fri Jul 12 2024 .SYNOPSIS... There will be a gradual and slow cooling trend through the middle of next week. Monsoonal moisture will increase for this afternoon into Saturday, then decrease for Sunday into Monday. There is a slight chance of showers and thunderstorms for this afternoon and early evening for the San Bernardino County mountains and deserts with greater chances for the mountains and deserts for Saturday afternoon and early evening. Decreasing chances for thunderstorms for the mountains and deserts on Sunday, then drier through Wednesday. Night and morning coastal low clouds will continue to extend inland into the western valleys at times late each night. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .SHORT TERM (Today through Sunday)... An increase in monsoonal like moisture from the Pacific will continue to stream in to Southern California from the south through this weekend. The interaction between the large scale ridge of high pressure over the Four Corners and weak low off the California coast will allow for this to occur through the weekend, though the peak of moisture and associated thunderstorm potential will likely occur on Saturday. Showers and thunderstorms Friday afternoon and evening will generally be widely scattered over the mountains and nearby deserts. Some elevated convection could occur Saturday morning, but the bulk of any convective activity will likely be in the afternoon hours around and after peak heating. The most favored locations appears to be the mountains of San Bernardino County, where there is around a 45 percent chance for 0.01 inch or more of rainfall, around a 25 percent chance for one- quarter inch or more, and a less than 10 percent chance for one- half inch or more. There is a 15 to 25 percent chance of showers and thunderstorms for the mountains and deserts for Sunday afternoon. && .LONG TERM... Drying and slow cooling will continue through the middle of next week. With the cooling, high temperatures on Wednesday will be a few degrees above average for the deserts and a few to around 5 degrees below average for the coast, valleys, and mountains with high temperatures in the lower deserts around 112 and for the Inland Empire mostly in the 90s. There is the potential for a greater influx of monsoonal moisture for late next week depending on the placement of high pressure over the Great Basin and southwest states into northern Mexico. Those that extend farther south with the high would have less potential for an influx of moisture into southwestern California while those that don`t extend as far south would have more potential for a greater influx of moisture. && .AVIATION... 122040Z...Coast/Valleys... Low clouds with bases 600-1000 ft MSL and tops around 1400 ft MSL over the coastal waters and extending locally inland. Low clouds returning to coastal TAF sites after 13/02Z this evening with similar bases and tops. Areas of fog with VIS 2-4 miles, locally 1 mile on higher coastal terrain and portions of the inland valleys late. Confidence in the arrival time of BKN- OVC low clouds at KSAN this evening per the TAF is moderate-to-high. Mountains/Deserts...FEW to SCT200 through today. Localized VIS reductions down to 3SM due to smoke in the San Bernardino Mountains VCNTY the Vista fire. Periods of northwest winds gusting to 30 kts in the San Gorgonio Pass through this evening. && .MARINE... No hazardous marine conditions are expected through Wednesday. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Excessive Heat Warning until 9 PM PDT this evening for Apple and Lucerne Valleys-San Gorgonio Pass Near Banning. Excessive Heat Warning until 9 PM PDT Saturday for Coachella Valley-San Diego County Deserts. PZ...None. && $$ PUBLIC...Suk/17 AVIATION/MARINE...Small