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Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
055 FXUS66 KSGX 110937 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 237 AM PDT Sun Aug 11 2024 .SYNOPSIS... Slightly cooler today with continued chances of thunderstorms over the mountains and deserts. Lower thunderstorm chances on Monday with any activity limited to the mountains. Drier with near normal temperatures Tuesday through the end of the week. Patchy low clouds and fog will gradually increase for the coastal areas each night and morning. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Low clouds remain off the coast this morning and will be patchy at best at the beaches later this morning. Elsewhere there are scattered high clouds developing ahead of the upper low to our south. A gulf surge is well underway with dew points climbing into the low 70s across the Imperial and Coachella Valleys. The upper low and associated inverted trough will slowly move across the Baja Peninsula today. While Precipitable Water doesn`t change much, this wave should help increase instability due to minor cooling aloft. Hi-res guidance continues to show more widespread and stronger convection along the mountains and locally into the deserts this afternoon, which could produce locally heavy rain, gusty winds, and lightning. Precipitation chances were increased to around 25-40 percent for the mountains and 20-25 percent for the deserts this afternoon and early evening. Otherwise today will be much cooler, especially in the low deserts, with highs near seasonal normals. Mid and upper level flow begin to turn westerly on Monday, bringing drier air in. There may be just enough residual moisture for isolated convection over the mountains, but chances are much lower - generally around 10-20 percent. A weak trough pushes through CA on Tuesday, which will continue the drying trend and bring breezy west winds to the mountains and deserts during the afternoon and evening. The weather pattern for much of the week can be described as weak troughing to our north pushing into the weak upper high over the East Pac that extends into So Cal. By the weekend the ridge gets pushed west as more amplified troughing develops along the West Coast. This will maintain high temperatures near normal through the week with minor cooling Friday into next weekend. The marine layer will gradually rebuild with areas of night and morning low clouds and fog along the coast and extending locally into the far western valleys. && .AVIATION... 110930Z...Coast/Valleys...Mostly clear skies with some FEW-SCT clouds near 20K ft MSL through early morning. Low clouds based near 700-1100 ft MSL offshore may impact coastal TAF sites between 12-16Z this morning with low confidence on exact coverage. If clouds do come ashore, local VIS 3-5 miles on higher terrain will occur. 10% chance of ISO TSRA drifting into foothills and adjacent valleys west of the mountains this afternoon; highest chance in SD County. Low cloud coverage confidence higher (50-70%) in cigs reaching coastal TAF sites later tonight, mainly after 06Z Mon based near 1000 ft MSL. Mountains/Deserts...SCT-BKN clouds with bases around 10,000 ft MSL develop after 16Z, followed by a 20-35 percent chance of TSRA between 19Z Sunday and 03Z Monday. Gusty and erratic winds possible near storms as well as MOD UDDFS. && .MARINE... No hazardous marine conditions are expected through Wednesday. && .SKYWARN... Skywarn activation is not requested at this time but may be needed this afternoon. Weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ PUBLIC...SS AVIATION/MARINE...APR