Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
663 FXUS66 KSGX 131034 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 334 AM PDT Sat Jul 13 2024 .SYNOPSIS... There are chances of thunderstorms in the mountains, locally into the deserts today and Sunday afternoon and early evening. Isolated chances of thunderstorms will continue in the mountains on Monday. Hot conditions will continue for the lower deserts into next week. Away from the deserts, temperatures will be near to slightly below average this weekend into the middle of next week. A gradual warming trend is expected for the middle to end of next week. Night and morning coastal low clouds will continue to extend inland into the western valleys into next week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Visible satellite imagery at 3 AM was showing low clouds have filled in along the coast and into the western valleys. Even with increased mid-level moisture this weekend, high resolution local guidance is indicating that low clouds will continue along the coast and western valleys each night and morning into next week. Areas of mid to high level clouds are expected this weekend, especially near the mountains. Scattered thunderstorms are likely in the mountains, locally into the deserts each afternoon and early evening this weekend. There are more isolated chances of thunderstorms in the mountains on Monday. Chances of thunderstorms developing early this morning have decreased, with the best chances this afternoon and early evening. Increased monsoonal moisture this weekend, combined with an upper level low moving north up the California coast, afternoon heating, and the sea breeze will generate enough instability and lift for thunderstorms in the mountains. Southeast flow aloft has the potential to push thunderstorms into the foothills and deserts today. There is even a potential (15-18 percent chance) for thunderstorms to develop along the Elsinore Convergence Zone in the Inland Empire this afternoon. For Sunday, thunderstorm chances become most likely over the mountains and in the High Desert. Locally heavy rain, frequent lightning, and gusty winds are the main concerns where thunderstorms develop. Critical fire weather conditions are expected in the San Bernardino and Riverside county mountains and High Desert due to the potential for dry lightning, more details can be found in the Fire Weather discussion below. High temperatures for areas away from the deserts will become near to slightly below average for this time of year this weekend through the middle of next week, with continued above average conditions in the deserts. HeatRisk in the High Desert decreases Sunday, with area of major HeatRisk continuing in the low deserts into much of next week. Highs in the low deserts on Sunday will fall a few degrees, but the increase in moisture will result in muggy conditions. Around the middle of next week, temperatures will gradually begin to increase for all areas into next weekend. && .AVIATION... 130935Z...Coast/Valleys...Low clouds have spread locally 15-20 miles inland at this hour and will continue to increase in coverage through 15Z. Bases are 900-1100 ft MSL with tops to 1800 ft MSL bases may lower to around 700 ft MSL 12Z-15Z. Local VIS 1-3SM on higher coastal terrain and portions of the valleys. Expect clearing to the coast 16Z-19Z and low clouds spreading inland again after 03Z Sunday. ISOLD-SCT TSRA could move into the valleys from the mtns this afternoon/evening but confidence is low for impacts at TAF sites. Mountains/Deserts...ISOLD-SCT TSRA this afternoon and evening in the mountains with SCT-BKN120. Brief, heavy rainfall and gusty and erratic winds likely with any storm. Mod up/downdrafts possible near the mountains. Low confidence for TSRA impacts at TAF sites at this time. Localized VIS of 3SM due to smoke in the San Bernardino Mountains VCNTY of the Vista fire. Gusty west winds possible up to 30kts around San Gorgonio Pass this afternoon and evening. && .MARINE... No hazardous marine conditions are expected through Thursday. && .FIRE WEATHER... A Fire Weather Watch continues for today and Sunday. Critical fire weather conditions from chances of dry lightning are expected for the San Bernardino and Riverside County mountains and High Desert this weekend. An influx of moisture will bring chances of thunderstorms to the mountains, locally into the deserts today and Sunday. Isolated chances continue in the mountains for Monday. Where cells develop, wetting rain is expected but lightning has the potential to strike up to 15 miles away from a thunderstorm. If lightning strikes away from wetting rain, fire starts are possible due to very dry fuel conditions. Strong and erratic winds are expected near where thunderstorms develop. Gusts 35 to 50 mph are possible. Strong and erratic wind gusts near thunderstorms have the potential to cause rapid spread of ongoing or new fires. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Fire Weather Watch from 9 AM PDT this morning through Sunday evening for Riverside County Mountains-Including The San Jacinto Ranger District Of The San Bernardino National Forest-San Bernardino County Mountains-Including The Mountain Top And Front Country Ranger Districts Of The San Bernardino National Forest-San Gorgonio Pass Near Banning- Victor Valley -Apple Valley -Lucerne Valley -Johnson Valley. Excessive Heat Warning until 9 PM PDT this evening for Apple and Lucerne Valleys. Excessive Heat Warning until 9 PM PDT Sunday for Coachella Valley-San Diego County Deserts. PZ...None. && $$ PUBLIC/FIRE WEATHER...CO AVIATION/MARINE...PG