Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
733 FXUS66 KSGX 171019 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 319 AM PDT Thu Jul 17 2025 .SYNOPSIS... Monsoonal moisture will increase today, decrease slightly on Friday, with a greater decrease over the weekend. This will bring a chance of showers and thunderstorms through Friday, mostlikely over the mountains and during the afternoons. Drying is expected during the weekend through the middle of next week. High temperatures for the deserts will be a few degrees cooler for today and Friday, a few degrees warmer for the weekend, with most areas a few degrees cooler for early next week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .SHORT TERM (Today through Saturday)... The precipitable water value on the NKX sounding late Wednesday afternoon was 1.29 inch. ECMWF ensemble output shows precipitable water values peaking late this afternoon, decreasing slowly on Friday, with a greater decrease for Saturday and Sunday. While the marine layer depth is not much different from 24 hours ago, marine layer cloud cover is much reduced over land areas of southwestern California and the coastal waters of San Diego County. Some patchy coverage of low clouds may return near the coast around sunrise, but not extend inland much past the coast. Satellite imagery shows more extensive mid and high cloudiness across southwestern Arizona moving slowly westward into the lower deserts of southern California. This cloud cover is associated with a Mesoscale Convective Vortex that has been moving slowly westward across southern Arizona. There have been showers and isolated thunderstorms overnight with this MCV with the more widespread showers on the northern side of the MCV. For today, increasing mid and high cloud cover may limit daytime heating with afternoon convection more elevated and less tied to terrain with lesser chances for thunderstorms and isolated heavier rainfall. For Friday, there may be greater clearing of the mid and high clouds, but with sufficient remaining moisture for thunderstorm development over the San Bernardino Mountains and Riverside County mountains during the afternoon with isolated brief heavier rainfall. High temperatures for today and Friday will be a few degrees cooler for the deserts with today the likely cooler day. Drying with warming for the deserts will begin on Saturday with only a 10 to 15 percent chance for afternoon showers or thunderstorms for the mountains on Saturday afternoon as the monsoonal moisture decreases. && .LONG TERM (Sunday through Wednesday)... Drying will continue for Sunday into the middle of next week. The deserts will warm a few more degrees on Sunday with most areas a few degrees cooler for early next week. Night and morning coastal low clouds will spread into portions of the western valleys late each night. && .AVIATION... 170930Z....Coast/Valleys...Patchy low clouds along the immediate coast based 1200-1800 ft MSL are expected to become slightly more widespread towards 11Z, but confidence in impacts at coastal sites is low. There is a 65% chance for BKN-OVC cigs at KSAN and KCRQ by 13Z this morning, with lower chances at KSNA. Any clouds will scatter 16-17Z this morning. Still patchy clouds, but likely more widespread than tonight, with similar bases will push ashore after 18/04Z. Otherwise, 15-20% chance for thunderstorms and rain showers to move westwards off the mountains into the eastern valleys, best chances 18-01Z today and increasing clouds 10000-15000 feet. Mountains/Deserts...Increasing clouds 10000-15000 feet today. ISO- SCT SHRA/TSRA over the mtns after 18Z today, with slight chance TSRA for the deserts. Highest chances through late this afternoon, but an isolated storm is possible overnight. Associated wind gusts, UDDFS, and VIS restrictions possible with any storm that develops. && .MARINE... No hazardous marine conditions are expected through Monday. && .BEACHES... A moderate period south-southwesterly swell (2-3 feet at 15-16 seconds) will continue to generate elevated surf and a high risk of rip currents through today. Surf of 3-5 feet expected with sets to 6 feet possible, primarily on southerly facing beaches. Swell and surf will begin to lower on Friday. && .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...17 AVIATION/MARINE/BEACHES...CSP