918 FXUS66 KSGX 170420 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 920 PM PDT Wed Apr 16 2025 .SYNOPSIS... Cooler, cloudier, and windier conditions expected through Friday. Periods of scattered light showers are expected tonight into Thursday morning and Thursday night into Friday morning. Dry and warmer conditions expected for the weekend into early next week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... This evening...The marine layer is now almost 7,000 ft deep, and layered clouds with bases from 3,500 to 7,000 ft cover the region from the mountains to the coastal waters. Sfc pressure gradients are trending stronger onshore with 10.0 mb SAN-TPH. The wind-prone locations in the mountains and desert slopes are currently gusting 45-65 mph. Locally strong winds in the mtns and deserts will continue through Thursday. From previous discussion... The marine layer will remain deep through Friday, with widespread low cloud coverage across the coastal basin each night. Cool conditions will continue Thursday with highs in the inland valleys 10 to 15 degrees below average. A low pressure system from the west will weaken as it moves through Southern California, bringing a chance for light showers late tonight into Thursday morning for the mountains westward. A second low pressure system from the north will follow Thursday night into Friday, bringing additional chances of showers. Recent guidance shows a slight inland shift to the track of that system, resulting in a slightly drier solution. Overall, rain will be light with rainfall rates 0.10 inches per hour or less for both passing systems. Through Friday evening, rainfall and liquid- equivalent above the snow level could range from less than 0.10 inch near the coast to 0.25 to 0.50 inch in the mountains, locally up to 0.75 inches. The snow level will fall to around 6500 feet on Friday with an inch or two of snowfall possible above 7000 feet. Over the mountains and into the deserts, the increased onshore pressure gradient from the passing lows will produce periods of gusty southwest to west winds through Friday night. Peak gusts 40 to 55 mph with isolated gusts to 65 mph are expected, most likely through passes. Strongest winds will occur Thursday, but wind speeds will remain elevated into Friday. Dry weather is expected with warming conditions for the weekend into early next week for the mountains and deserts. Coast and valley locations will remain dry but may cool a degree or two for early next week. With the warming, high temperatures on Sunday will range from the mid to upper 60s near the coast to the mid 70s to lower 80s for the Inland Empire with the lower deserts around 90. Overall, high temperatures will mostly be within around 5 degrees of average for Saturday through Tuesday. && .AVIATION... 170310Z....Coasts/Valleys/Foothills...BKN-OVC clouds near 5000-6000 ft MSL will continue this evening. Cigs will lower near 3500-4500 ft MSL sometime after 06Z as the chance of VCSH increases through the area. Cigs may near 3,000 ft in any isolated showers that arise until 17-19Z Thu, locally continuing into the afternoon near the foothills. Otherwise, BKN-OVC for most areas with cigs near 5,000-6,000 MSL for much of the day on Thursday. Higher Mountains/Deserts...FEW-SCT high clouds through tonight. Westerly and southerly winds will continue to be gusty through tonight into Thursday night with widespread gusts 25-40 kts, locally up to 55 kts in and below passes. Strong up/downdrafts and isolated LLWS in lee of mountains such as vcnty KPSP. Winds will remain elevated through Friday, especially in the RIV/SD Co mountains. && .MARINE... No hazardous marine conditions are expected through Monday. && .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...APR