Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
794 FXUS66 KSGX 110435 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 930 PM PDT Fri May 10 2024 .SYNOPSIS... Areas of night and morning low clouds and fog will continue across portions of the coastal areas and valleys through the next week. Gradual warming inland will occur through Sunday followed by minor cooling Monday and Tuesday. Inland warming trend will likely resume the second half of next week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Update... Some convection formed over mainly San Bernardino County this afternoon which caused some virga or local light showers but more notably caused some gusty winds, locally over 40 MPH, mainly around 5 PM. Skies had cleared over most of the mountains and deserts by mid-evening, with widespread stratus in coastal and some of the valley areas. The Mojave Desert upper low that brought that convection today will slowly move east and be over the Four Corners region by Saturday afternoon with mostly weak gradients to follow over SoCal. Models/ensembles generally have a weak closed low off the coast early next week which could bring some cooling. Otherwise, May will be May-like with coastal stratus, especially during the nights and mornings but lingering at least during some afternoons near the coast for the next several days and likely beyond that. From previous discussion... Low clouds have stubbornly hung on in coastal San Diego County early this afternoon, and it doesn`t look so good for clearing today. Low clouds have cleared elsewhere just fine. Cumulus clouds have accumulated in the mountains and deserts, but so far they haven`t grown tall enough to produce showers. A weak upper level trough sits over the West today, with a wave of mid-level moisture and instability rotating through inland SoCal. This feature is the cause of the cumulus clouds over the mountains and deserts, leading to a slight chance of showers to the higher mountains through early evening. The trough begins to weaken and move out over the weekend, but with lingering moisture and some clouds over mountains in the afternoon. The trough`s departure will bring us a warming trend, and a shallower marine layer for less nocturnal cloud/fog extent Sunday into Monday. A new weak upper low from the northwest will float harmlessly across SoCal Monday and Tuesday, which should deepen the marine layer and extend the coastal clouds. Today we`ll have max temps a few degrees below normal except inland valleys should reach a little above. We warm up this weekend, so that by Sunday max temps should be 0-8 degrees above normal. The 0-degree difference representing the coast and the 8-degree difference in the low desert, probably hitting 100 degrees in spots. For the second half of next week, there is unsurprisingly a large spread in ensemble guidance. An amplified high-pressure ridge develops over the West, but with a weak low-pressure trough directly south of it, what we call a Rex Block. SoCal lies within the lower pressure embedded under the strong high pressure, so the forecast picture gets wishy- washy. A slimming minority of members indicate some low pressure and moisture leading to showers, but the vast majority of members keep our weather dry and seasonal. For now our forecast Wednesday through next Friday is dry with a warming trend, a typical medium strength marine layer, and temperatures near normal at the coast and a few degrees above normal inland. && .AVIATION... 110400Z...Coast/Valleys...Areas of low clouds with bases around 2000 ft MSL and tops to 3300 ft MSL increasing in coverage at this hour. CIG impacts currently at coastal TAF sites likely to reach KONT and KSBD around 07Z. Bases may lower by a few hundred feet between 09Z and 15Z. Low clouds likely to reach the coastal slopes by 13Z, obscuring higher terrain, with VIS 1-3SM in fog where clouds and terrain intersect. Expect inland clearing 16Z-18Z and partial clearing at the coast after 18Z. SCT-BKN low clouds could persist at the beached into Sat afternoon. Mountains/Deserts...Mostly clear with unrestricted VIS through Sat morning. SCT/BKN clouds over the mountains with bases around 9000 ft MSL Sat afternoon. && .MARINE... No hazardous marine conditions are expected through Tuesday. && .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...Maxwell (Update)/MM (Previous Discussion) AVIATION/MARINE...PG