Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
290 FXUS66 KSGX 021018 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 318 AM PDT Sun Jun 2 2024 .SYNOPSIS... Night and morning low clouds will continue west of the mountains this week, with patchy drizzle possible this morning and again Monday morning. A warming trend will occur Monday through Thursday, with moderate heat risk developing in the deserts. Cooler with increasing onshore flow late next week into the weekend. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... At 3 AM, low clouds were extensive across the coastal basin. Drizzle has been reported across coastal Orange County over the past few hours, and patchy drizzle will continue for areas west of the mountains through mid-morning. Inland areas should slowly clear by late morning, but low cloud cover will likely persist across the coast through much of today. A more shallow marine layer is expected through the upcoming week, but night and morning low clouds will likely still continue each day west of the mountains. Highs will generally remain below normal today with the exception of the deserts. Southern California will be on the periphery of multiple systems this week, with an anomalously strong trough moving into the Pacific Northwest early this week, a weak closed low forming to the west of Baja California, and a building ridge centered over the Great Basin by midweek. A warming trend develops region-wide on Monday and highs will warm a few degrees each day through Thursday. The deserts will feel the brunt of the heat this week, with moderate heat risk developing by Tuesday. Wednesday and Thursday look to be the hottest days of the week, with highs approaching 110 in the lower deserts, and the mid-100s in the High Desert. Highs in the valleys and the mountains will run 5-10 degrees above seasonal averages, and the coast will continue to be moderated by the persistent marine layer. Ensemble guidance begins to diverge in the placement of the ridge axis toward the end of the work week, as well as the timing of when the closed low to our southwest will become absorbed into the mean flow. At this time, ECMWF ensemble members are showing the weakening low passing over Southern California Friday or Saturday, enhancing onshore flow, spreading cooling inland and increasing moisture over the region. How this evolves over the coming days will determine whether there could be enough moisture and instability to initiate isolated convection, or just lead to increasing high clouds. && .AVIATION... 020900Z...Coast/Valleys...BKN-OVC low clouds with bases 1500-2500 ft MSL with tops to 3000 ft MSL have filled in the coastal basin as of 09Z. VIS restrictions on higher terrain where clouds and terrain intersect. 40% chance of VIS restrictions 2-5SM in the eastern valleys including KSBD 12-16Z. Expect clearing in the valleys 16Z- 19Z and partial clearing near the coast 18Z-21Z. SCT-BKN clouds with bases 1500-2000 ft MSL near the coast through this afternoon. Low clouds will spread back inland after 02Z Mon, with similar bases. Mountains/Deserts...Clear skies with unrestricted VIS today. West winds gusting up to 40 kt will occur again 22Z Sun-10Z Mon from the mountain crests east through the desert slopes and into the deserts, including through/near San Gorgonio Pass. Gusts 25-30 kt near KPSP and KTRM. MOD UDDFS expected. && .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...None. PZ...None. && $$ PUBLIC...EA AVIATION/MARINE...CO