Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
521 FXUS66 KSGX 232103 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 203 PM PDT Sun Jun 23 2024 .SYNOPSIS... Hot conditions will continue today, with widespread moderate to locally major heat risk. There is a slight chance of showers and isolated thunderstorms this afternoon for the mountains. Temperatures west of the mountains will gradually decrease into next week, but the heat will remain through Thursday in the deserts. Slight chances of isolated showers and thunderstorms remain over the San Bernardino and Riverside mountains, locally into the High Desert Monday afternoon. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Visible satellite this afternoon was showing plenty of low topped cumulus have develop along the mountains. As of 2 PM no shower or thunderstorm activity had been detected. High resolution guidance continues to be bullish with shower development this afternoon. The most likely scenario is a shower or thunderstorm could develop late this afternoon but coverage would be very isolated and confined to the mountains, possibly in the High Desert. Model guidance is showing the moisture over Southern California very slowly decreasing into Wednesday. Guidance is also indicating the atmosphere will slowly stabilize into Wednesday as drier air moves in aloft in more westerly flow. Current forecast leaves chances of isolated showers and thunderstorms in the San Bernardino and Riverside mountains into portions of the High Desert Monday afternoon. High resolution models are also very bullish about shower and thunderstorm development Monday, but enough moisture and lingering instability will be present for an isolated shower or thunderstorm to develop. A Pacific trough will slowly move into the Pacific Northwest this week, weakening the ridge currently over the Southwest. As a result temperatures west of the mountains will fall a couple degrees each day Monday through Thursday. By Thursday, even the deserts will see a few degrees of cooling. As the trough approaches and the influence from the ridge weakens, the marine layer will be able to rebuild. By mid-week night and morning low clouds should return to the coast, locally into the western valleys. && .AVIATION... 231950Z...Coast/Valleys...The very patchy marine layer low cloud pattern is expected to continue through Monday. SCT bases 700-1000 ft MSL coastal waters and locally onshore 12z - 17Z. Tops will be 1200 ft MSL. Otherwise, SCT locally BKN clouds mostly at/above 9000 ft MSL through this evening. Mountains/Deserts...There is a 20-30 percent chance of TSRA between 17Z and 04Z Sun and Mon, with CB tops to 35000 ft MSL and possible strong up/downdrafts and local surface wind gusts over 30 kt. Otherwise, SCT-BKN clouds mostly at/above 9000 ft MSL through this evening. Local west winds with gusts 25-35 kt will develop after 22Z, continuing this evening on the desert mountain slopes and into the deserts. && .MARINE... No hazardous marine conditions are expected through Thursday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Heat Advisory until 8 PM PDT this evening for Orange County Inland Areas-San Bernardino and Riverside County Valleys- The Inland Empire-San Diego County Valleys. Excessive Heat Warning until 8 PM PDT Thursday for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts- San Gorgonio Pass Near Banning. PZ...None. && $$ PUBLIC...CO AVIATION/MARINE...Small