Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
383 FXUS66 KSGX 221640 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 940 AM PDT Tue Apr 22 2025 .SYNOPSIS... Night and morning low clouds are expected each day at the coast into the valleys through the week. Increased sea breeze winds are expected each afternoon and evening for the mountains and deserts, stronger westerly winds expected over the weekend. Areas of drizzle or light rain are possible west of the mountains over the weekend. A cooling trend will continue through the end of the week. Gradual warming is expected next week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Low clouds this morning made it well into the coastal basin. Low clouds are starting to clear from the valleys at 9 AM. It`s looking like low clouds will clear most areas this afternoon, but will quickly move back inland early this evening. The marine layer should deepen tonight, likely filling in the entire coastal basin as a trough deepens and moves across the Pacific Northwest. In addition to widespread cloud coverage, westerly winds will be elevated Wednesday afternoon and evening through passes and locally into the deserts. Highs today will be around 4 to 8 degrees above average for the deserts into the mountains. Highs for the coast and valleys will be as much as 5 degrees below average. Highs on Wednesday will be fairly similar, with a few degrees of cooling in the mountains and deserts. The cooling trend will continue into Thursday, with highs in the deserts falling to near average with the western valleys and inland Orange County around 4 to 8 degrees below average. Friday through the weekend a deeper low will move across the West Coast. Ensemble guidance is in better agreement in the track of the low compared to 24-hours ago. By Saturday, the majority of ensemble clusters indicate the trough will dig into either northern or central California. That will bring a more significant cooling, with the potential for stronger winds for the mountains and deserts, and even some light precipitation or drizzle to areas west of the mountains. Timing wise, the trough is expected to pass through Southern California Saturday evening into Sunday. NBM chances for wind gusts reaching or exceeding 45 mph on Saturday afternoon and evening are around 90 percent for the mountain passes and 50 to 60 percent for the deserts. NBM chances for measurable precipitation (at least 0.01 inches) Saturday into Sunday are 5 to 10 percent for the coast and valleys and up to 25 percent for the coastal mountain slopes. NBM seems to be on the more pessimistic side of the probability of precipitation with GFS and ECMWF MOS having chances for measurable precipitation higher and more consistent with the pattern, around 15 percent near the coast to 20 to 30 percent in the mountains. Dry with a warming trend for early next week with Tuesday high temperatures warming to around average. The marine layer will become shallower with coastal low clouds not extending as far inland. && .AVIATION... 221530Z....Coasts/Valleys...Low clouds based 1500-2000 feet MSL with tops to 2500 feet and VIS reductions 0-5 SM in BR for inland valleys and on higher coastal terrain. These will lift and clear this morning, scattering out by 17-18Z. Low clouds at 1800- 2200 feet MSL will push ashore after 03Z and fill the coastal basin overnight, with vis reduced far inland and against coastal foothills. Scatter out Wednesday 17-19Z. Otherwise...mostly clear through Tuesday morning. && .MARINE... No hazardous marine conditions are expected through Saturday. && .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...CO AVIATION/MARINE...MM