Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
278 FXUS66 KSGX 100945 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 245 AM PDT Fri Oct 10 2025 .SYNOPSIS... A low pressure system off the West Coast will continue to draw moisture from Tropical Storm Priscilla northward into the area through Saturday morning, with chances for showers and thunderstorms at times. Cooler with drying and a return of the marine layer early next week. For Tuesday and Wednesday of next week, a low pressure system moving southward along the West Coast will bring a chance of showers along with stronger westerly winds. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... This morning, a band of light showers extends from the coastal waters near San Clemente island to the high deserts northeast of Big Bear. The band as a whole is slowly drifting northward even as the elements move to the northeast in the mean flow around the base of a trough extending from a low pressure system centered off the Oregon coast. So far, rainfall amounts have been light, ranging from a trace to about two tenths inch in the last 12 hours. While the bulk of the moisture from what is still Tropical Storm Priscilla remains to our east and south, there is no shortage of moisture over SoCal, with about 1.4 inches of precipitable moisture. What we seem to lack is a deep, unstable layer and a mechanism for forcing deep convection. Moisture from Priscilla will continue to be drawn into SoCal through late tonight or early Saturday morning, continuing the chances for showers and tstms. Chances for tstms with locally heavier rainfall increase over the mtns and deserts late today as Priscilla`s upper level circulation is drawn into the mean southwesterly flow becoming an open wave by this afternoon and all but vanishing in the circulation around the low to the northwest by Sat morning. Overall, precipitation is not expected to be heavy but locally heavy rainfall in tstms can`t be ruled out due to the amount of available moisture. Fair and cool weather is expected from late Sat through Monday under cyclonic flow aloft. Onshore flow will strengthen late Sat into Sun morning as the low moves inland to the north. Winds will peak Sat evening with localized gusts of up to 50 mph in the favored mtn passes and adjacent desert areas. The marine layer low clouds and fog could make a return as soon as Sat morning but more likely for Sunday and Monday mornings. For next Tue and Wed...Model solutions begin to diverge on Monday as a reinforcing shortwave trough moves southward out of western Canada into the mean trough over the western US. Beyond Monday, forecast details are uncertain due to significant spread in the model solutions with respect to the timing and placement of the low pressure system as it forms a closed upper low near WA/OR on Monday then moves southward along the coast, reaching SoCal on Wed. Depending on which solution verifies best, we could be cold, windy and wet for Tue-Wed or we could be cold, windy and not so wet. There is a small chance for a dusting of snow on Tue in the San Bernardino Mtns above 7,500 ft but it`s not something I would plan on at this point. The low/trough moves inland toward the end of next week and fair weather will likely return but the timing remains uncertain. && .AVIATION... 100930Z....BKN clouds based 8000-12000 feet MSL with ISO -SHRA region-wide today and tonight, and ISO-SCT SHRA/TSRA inland 18-04Z. Any TSRA could lower cloud bases to 5000 feet MSL briefly, and could bring gusty winds and reduced vis in +RA. Decreasing clouds and -SHRA overnight into Saturday, but patchy coastal low clouds based around 1000-2000 feet MSL to develop after 08Z into Saturday. && .MARINE... Northwest wind gusts occasionally exceeding 20 knots around San Clemente Island during the afternoons and evenings today and Saturday. No hazardous marine conditions are expected today 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...PG AVIATION/MARINE...MM