Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
065 FXUS66 KSGX 221718 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 918 AM PST Fri Nov 22 2024 .SYNOPSIS... Warm and dry weather prevails today with generally clear skies and mostly light winds. An atmospheric river currently over Northern California shifts southward on Saturday, increasing moisture and cooling temperatures. Very light precipitation is expected as early as Saturday night/Sunday morning, with slightly better chances for rain Monday through Wednesday. Any rain will move out by late Wednesday, with warmer and drier conditions returning for the end of next week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .Morning Update... Generally sunny skies and light winds prevail today before a more expansive and deeper marine layer builds inland tonight. Even as the marine layer dissipates late Saturday morning, increasing cloud cover ahead of an atmospheric river will encompasses most of the region, cooling temperatures on Saturday by 5-10 degrees over Friday. While moisture increases this weekend, the AR substantially weakens as it reaches Southern California, and only light precipitation is expected Saturday night into Sunday. Even in the mountains, where snow levels look to remain above 6800 through the weekend, precipitation totals will be minimal with only up to 0.25" forecasted. Despite the decreasing trend in rain amounts, another surge of moisture Monday and Tuesday will bring additional chances for precipitation across Southern California, especially for the higher terrain. At this point models are still somewhat spread on chances for early next week and how far south the rain will make it. Regardless, temperatures should remain below normal through Wednesday before weak upper ridging brings warmer weather for the end of next week. .Previous Discussion (401 AM PST Thursday)... Skies are clear again this morning, but there are a couple patches of low clouds and fog along the coast. These will continue to develop at the coast, but the day will be mostly sunny. Onshore flow increases today, bringing cooler weather west of the mountains as the marine layer rebuilds. More widespread low clouds will develop and push ashore early this evening and move locally inland by Saturday morning. An atmospheric river that has been dropping copious rainfall on Northern California will gradually sag southward today and Saturday. The moisture plume and energy seem to fizzle somewhat on its southward journey. Skies will cloud up Saturday with chances of light rain becoming widespread. With no discernible trigger mechanism for getting that moisture to turn into rain, the mountains will use their orographic power to harvest the most rain. Except for isolated foothills, there won`t be heavy or prolonged rainfall. Snow levels will be way up, above 9,000 feet Saturday, but dropping to around 7,000 feet by early Sunday. Snowfall will not accumulate in mountain communities. This won`t be a particularly windy system. The mountain ridges will get some strong gusts of 30-40 mph, but lower elevations won`t get strong winds. Sunday is trending drier with recent model guidance. Overall, we`re in a moist pattern and waves of moisture will come and go for several days. Another plume of moisture arrives in SoCal Monday through Tuesday. Pinpointing when and where rain will fall next week is a tough problem. A broadbrush approach is probably best, with chances of mostly light rainfall Monday into early Wednesday. Our moist zonal pattern seems to buckle around Wednesday or Thursday, which would put SoCal in a transient ridge and its corresponding dry weather. Of course by that time there is a big spread in model solutions. There are hints the wet pattern could redevelop late next week, or we could stay dry for a while. && .AVIATION... 221600Z...Coast/Valleys...Patchy low clouds with bases 700-900ft MSL lingering along the coast this morning, but will clear now to 18Z this morning. Very brief CIGs at coastal sites are possible during this period. Much more widespread low clouds should push back ashore around 00Z-03Z Sat, with likely higher bases and spreading farther inland (15-25 miles) overnight. Mountains/Deserts...FEW-SCT clouds at or abv 20000 ft MSL and unrestricted VIS through this evening. && .MARINE... No hazardous marine weather conditions 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...Zuber/MM AVIATION/MARINE...CSP