Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
162 FXUS66 KSGX 092033 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 133 PM PDT Sun Mar 9 2025 .SYNOPSIS... Dry and warmer today with high temperatures reaching the mid seventies in the inland valleys, about 4 to 6 degrees above seasonal averages. Precipitation returns for Monday night into Tuesday and again for late Wednesday through Friday. There is greater potential for heavier precipitation, lower snow levels and widespread gusty west winds with the system late Wednesday through Friday. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... This afternoon...Sunny and warm with temperatures as much as 11 degrees higher than at this time yesterday in the inland valleys, and as much as 15 degrees warmer in a few mountain locations. Sfc pressure gradients remain weakly offshore and there are still localized easterly breezes in the mountain passes. From previous discussion... A low pressure system will move in from the west late Monday through Tuesday. There is still some spread among model solutions with respect to the timing and track of the closed upper low which will move inland over or just south of SoCal on Tue, becoming an open wave as the trough axis reaches the lower Colorado River valley Tue night/Wed morning. Due to the most likely timing of the eastward progress of the low, SoCal will be in the warm sector ahead of the low for most of Monday. As a result, high temperatures on Monday will be similar to today. Precipitation will likely begin to move in from the west Monday night, spreading north and east on Tuesday before tapering off Tue night. Rainfall/water equivalent accumulations will likely favor San Diego County where about one half to three quarters inch is expected in the local mountains and about one third inch is expected in the coastal areas and valleys. Areas farther north will likely receive significantly less rainfall. Snow levels will start out at about 6,500 feet on Monday, lowering to about 5,000 feet on Tuesday. Snow accumulations will be limited by the temperatures in San Diego County and by the lack of moisture in the Riverside County and San Bernardino Mountains. The possibility of thunderstorms cannot be ruled out but at this time tie probability is less than 15 percent. There will likely be a brief break in the precipitation on Wednesday as the first low pressure system moves east and a transient high pressure ridge moves in from the west ahead of a second system approaching from the northwest. Numerical models seem to be converging on a solution for this second system which will be colder with the potential to produce more widespread and greater amounts of precipitation. It will also produce widespread strong and gusty westerly winds. The winds will likely peak on Thursday with gusts of 55-65 mph in the mountains and adjacent desert areas. Precipitation will move in from the northwest Wed afternoon, spreading south and east through Thursday. Current estimates for rainfall totals/water equivalent are for about 2-3 inches in the San Bernardino and Riverside County Mountains, 1-1.5 inches in the Santa Ana and San Diego County Mountains, one half to three quarters inch in the coastal and valley areas, and about one tenth to one half inch in the deserts. The snow level will start out around 6,000-6,500 ft on Wed and lower to around 3,500-4,000 ft Thu afternoon. Most of the precip will likely fall Thu morning when the snow level is around 4,500-5,000 ft. The chances for thunderstorms are better with this system, mostly due to the colder air aloft and better dynamic forcing. Thursday seems to be the most favorable. This system moves east on Friday but a percentage of ensemble members continue to show chances for precip into Saturday even as a weak ridge tries to develop over the west coast. Next weekend could be mostly fair weather but models indicate that another low pressure trough is poised to move in early next week. && .AVIATION... 092030Z...Coast/Valleys...Patchy low clouds offshore again late tonight, with low chances (10-20%, highest in northern Orange County) of impacts over land. Otherwise, mostly clear and unrestricted VIS through Monday evening before another round of patchy low clouds will attempt to push ashore after 03z Tuesday. Mountains/Deserts... Mostly clear skies with unrestricted vis tonight and tomorrow. && .MARINE... No hazardous marine conditions are expected through late Wednesday. Southwest to west winds with gusts in excess of 20 knots likely Wednesday night into Friday, creating conditions hazardous to small craft. There is a 60% chance of wind gusts to 34 knots Thursday evening 30-60 nautical miles offshore with decreasing chances the closer you get to land. && .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...Zuber