Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
844 FXUS66 KSGX 121100 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 400 AM 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 today 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 moisture from the southeast is expected for today and Saturday with the moisture decreasing for Sunday into Monday. There will be a gradual and slow cooling trend for high temperatures for today through around Wednesday of next week. Night and morning coastal low clouds will continue to spread into portions of the far western valleys late each night. There is a slight chance for showers and thunderstorms for this afternoon and early evening, mainly for the San Bernardino County mountains and deserts with around a 20 percent chance for 0.01 inch or more of rainfall for the San Bernardino Mountains, a less than 10 percent chance for one-quarter inch or more of rainfall, and a 1 percent chance for one-half inch or more. While there could be some elevated convection for Saturday morning in the form of scattered showers and isolated thunderstorms, the more likely time and locations for showers and thunderstorms would be for the afternoon and early evening for the mountains and deserts with the greatest chances for the San Bernardino County Mountains. For the San Bernardino County Mountains on Saturday, 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 (Monday through Thursday)... 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... 120940Z...Coast/Valleys...Low clouds with bases 500-700 ft MSL and tops to 1400 ft MSL spreading inland could extend locally 15-20 miles inland by 15Z. Bases could go down to 300 ft MSL at times 10Z- 15Z. VIS locally 1-3SM in fog on elevated coastal terrain and some inland areas, otherwise VIS 3+ miles becoming unrestricted after 17Z. Expect clearing to the coast 16Z-18Z. Low clouds move ashore again after 00Z Sat with bases slightly higher. Mountains/Deserts...FEW-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. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .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...17 AVIATION/MARINE...PG