Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
537 FXUS66 KSGX 172041 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 141 PM PDT Wed Jul 17 2024 .SYNOPSIS... A gradual warming trend is expected into Saturday, leading to temperatures well above average this weekend. That will mean moderate to major heat risk for the valleys and major to extreme heat risk for the deserts. There are slight chances of showers and thunderstorms each afternoon in the mountains into early next week. Coastal low clouds and fog will continue to reach into portions of the western valleys each night and morning. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Cumulus buildups are percolating over the mountains this afternoon, but none have grown into thunderstorms yet. There`s still a slight chance before about 5 pm. Coastal clouds have clinged tenaciously to the coast in San Diego County, but it looks like they`ll clear later on. High pressure aloft currently over the four corners region will strengthen and migrate westward to the Great Basin over the next few days. Temperatures should climb a little each day into the weekend, gradually achieving 5-10 degrees above normal inland on Saturday. We have an Excessive Heat Watch for all deserts this weekend: Fri-Sun for lower deserts and Sat-Sun for the high desert. Temps decrease slightly next week, but not much. Monsoon moisture and instability will increase Thursday for a better chance of afternoon thunderstorms in the mountains and high desert. We`ve been advertising more monsoon action into the weekend in recent days, but recent and credible guidance indicates a decrease in moisture Friday through Sunday. We`ve updated the forecast to carry only a slight chance in the mountains during the afternoons Friday, and again Monday through Wednesday. That`s right, the weekend looks dry. If you`re interested in the mountain forecast, stay tuned as the monsoon messaging will probably continue to get adjusted. The marine layer and coastal cloud deck will diminish under the strengthening high pressure aloft over the next several nights and mornings. The geographical cloud coverage won`t back off that much, but the time spent under the cloud will. That will help the warming trend come to the coast this weekend, but only to a couple degrees above normal. The strong upper high over the Great Basin will not budge. No matter how many features may dampen or weaken it temporarily (looking at you Northwest trough), it is resilient, so keep planning for hotter than normal summer weather inland next week. && .AVIATION... 172030Z...Coast/Valleys...Areas of low clouds will continue with bases 1000-1500 ft MSL near the beaches this afternoon, mainly in San Diego County. Low clouds will develop within 10 miles of the coast 03Z-07Z Thu and spread up to 20 miles inland by 12Z Thu with bases 900-1300 ft MSL and tops to 2000 ft MSL and local VIS 3-5 miles in BR in the coastal valleys 08Z-17Z Thu. Clearing will occur 15Z-19Z Thu, with local BKN low clouds Thu afternoon near the beaches. Mountains/Deserts...Isolated SHRA/TSRA will occur through 02Z Thu. CB bases will be 10000-12000 ft MSL with tops to 3500 ft MSL. Gusty outflow winds and reduced VIS will occur in RA VCTY TSRA. && .MARINE... No hazardous marine conditions are expected through Monday. && .BEACHES... Long period 3 foot SSW swell (200-210 degrees) will bring elevated surf of 4-6 feet with sets up to 7 feet for south-southwest facing beaches in both Orange and San Diego counties and a high risk of rip currents at all beaches. A Beach Hazard Statement remains in effect through Thursday evening. Swell and surf will lower Friday, but the rip current risk will remain high. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement through Thursday evening for Orange County Coastal Areas-San Diego County Coastal Areas. Excessive Heat Watch from Saturday morning through Sunday evening for Apple and Lucerne Valleys. Excessive Heat Watch from Friday morning through Sunday evening for Coachella Valley-San Diego County Deserts-San Gorgonio Pass Near Banning. PZ...None. && $$ PUBLIC...MM AVIATION/MARINE/BEACHES...Maxwell