Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
032 FXUS66 KSGX 091753 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 1053 AM PDT Tue Jul 9 2024 .SYNOPSIS... The hottest days for the coast and valleys will be through Thursday with not much change for the mountains and deserts. An influx of monsoonal moisture over the weekend could bring a slight chance of afternoon and early evening showers and thunderstorms for the mountains and deserts. A gradual slow cooling trend will begin around Friday and continue into next week with Monday high temperatures within a few degrees of average. Night and morning coastal low clouds will spread into portions of 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... No Significant changes to the forecast this morning as the marine layer retreats towards the coast and heating and mixing take hold inland. previous forecast is on track with the hottest day of the heatwave occurring today through Thursday. Previous discussion 331 AM PDT Tuesday July 9 2024 The hottest days for the coast and valleys are expected for today through Thursday. Wednesday is the most likely hottest day with high temperatures for the inland valleys of 10 to 15 degrees above average, to 108 to 112 in the far inland valleys. There will be minor day to day differences in high temperatures for the mountains and deserts with widespread Extreme Heat Risk for the deserts. Night and morning coastal low clouds will spread into the far western valleys at times late each night. There will also be some afternoon clouds for the mountains. && .LONG TERM (Friday through Monday)... The center of high pressure over the southwest states will move slowly toward the north and east and in combination with a weak low pressure system off the California coast could draw some monsoonal moisture into the area from the southeast over the weekend. ECMWF ensemble output has the highest precipitable water values for Imperial over the weekend with continuing spread in the timing of drying for the early into the middle of next week. There is a slight chance for showers and thunderstorms for the mountains into the adjacent deserts each afternoon and early evening over the weekend. High temperatures will gradually cool through the weekend and early next week with Monday high temperatures generally within a few degrees of average. The marine layer will continue to moderate the heating near the coast with night and morning coastal low clouds extending into the far western valleys at times late each night. && .AVIATION... 091700Z...Coast and Valleys...Low clouds with bases 800-1200 feet AGL and tops to 1600 feet MSL were widespread have burned to the beaches just prior to 17 UTC. Strong upper ridge is over Socal through Wednesday and forecast indicates less coverage of the marine layer clouds tonight and Wednesday morning but extensive along the San Diego coast 10 to 15 UTC. The top of the marine layer is forecast to lower nearly 500 feet down to about 1200 feet MSL. Mountains/Deserts...Clear skies with unrestricted visibility will continue through tonight. West surface winds in mountain passes with gusts 20 knots after 22 UTC Tuesday through mountain passes. This will lead to weak to moderate up/downdrafts over and east of the mountains. There is smoke from the Vista wildfire near Mt Baldy and the Lake fire in Santa Barbara county. && .MARINE... No hazardous marine conditions are expected through Saturday. && .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 Thursday for San Bernardino and Riverside County Valleys-The Inland Empire- San Diego County Valleys. Heat Advisory until 9 PM PDT Thursday for Riverside County Mountains-San Bernardino County Mountains. Heat Advisory until 9 PM PDT Thursday for Orange County Inland Areas-Santa Ana Mountains and Foothills. Excessive Heat Warning until 9 PM PDT Thursday for San Diego County Mountains. Excessive Heat Warning until 9 PM PDT Friday for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts- San Gorgonio Pass Near Banning. PZ...None. && $$ PUBLIC...Suk/17 AVIATION/MARINE...Tardy