Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
131 FXUS66 KSGX 131752 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 1052 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... The fire weather watch for the San Bernardino Mountains, Riverside Mountains, adjacent foothills and high deserts has has been upgraded to a Red Flag Warning for the potential extreme fire weather created by dry lightning and associated gusty erratic winds that will exist near thunderstorms Today through Sunday Night. Thunderstorm activity is expected to peak around or after peak heating each day, but there is potential for some elevated convection to remain active through the overnight hours into Sunday. This is on track with the previous forecast package and no additional significant changes are anticipated at this time from the previous discussion. PREVIOUS DISCUSSION 334 AM Saturday July 13, 2024 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... 131625Z...Coast/Valleys...Low clouds with bases 900-1100 ft MSL with tops to 1800 ft MSL. 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 14/03Z Sunday with similar bases and tops. Mountains/Deserts...ISOLD-SCT TSRA with SCT-BKN120 with tops to FL300. Brief, heavy rainfall and gusty and erratic winds likely with any storm. Mod up/downdrafts possible near the mountains. 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. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Red Flag Warning until 9 PM PDT Sunday 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...Suk AVIATION/MARINE...Small