Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
441 FXUS66 KSGX 240415 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 915 PM PDT Sun Jun 23 2024 .SYNOPSIS... 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. Drier and warm conditions continue later in the week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .Evening Update... Elevated convection made a small appearance this afternoon across our forecast area with rainfall seen near Toro Peak and other spots across the high desert. Moisture and instability look to remain in place, though not as prevalent by Monday afternoon. This matches hi-res model thinking of minimal activity expected over the mountains and deserts for the period, with highest chances being near the higher peaks. Highs were once again well above average today along with some sweltering humidity. San Diego reached a high of 84 degrees this afternoon. The last time San Diego went into the 80s was back in November. Heat advisories for valleys west of the mountains are now expired as slightly cooler air will bring temperatures as well as humidity down, though warm temperatures will remain for much of this week. .Previous Discussion (203 PM Sunday)... 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 for 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... 240400Z...Coast/Valleys...Occasional SCT local BKN clouds at/above 12000 feet MSL will continue through Mon evening. Only patchy mostly SCT low clouds with bases 800-1100 ft MSL will occur 08Z-17Z Mon with less than a 20 percent chance of a CIG at any coastal airport. Most VIS will remain unrestricted through Mon afternoon. Areas of BKN low clouds and patchy fog could develop along the San Diego County coast after 04Z Tue. Mountains/Deserts...Occasional SCT local BKN clouds at/above 10000 feet MSL will continue through Mon evening with mostly unrestricted VIS. There is a 20 percent chance of TSRA over the mountains Mon afternoon, with CB tops to 30000 ft MSL possible, along with local strong up/downdrafts. && .MARINE... No hazardous marine conditions are expected through Friday. && .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 8 PM PDT Thursday for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts- San Gorgonio Pass Near Banning. PZ...None. && $$ PUBLIC...APR/CO AVIATION/MARINE...Maxwell