Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
460 FXUS66 KSGX 040434 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 934 PM PDT Sun Aug 3 2025 .SYNOPSIS... Near normal temperatures will occur through Tuesday. High pressure will strengthen over the region Wednesday through Friday, which will bring a warming trend across the area 5 to 10 degrees above average. The marine layer will become shallower by the middle of the week as well, keeping clouds and fog confined closer to the coast. There are increasing chances to see the high weaken by next weekend, bringing temperatures closer to average. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Update: Latest satellite imagery reveals that some of the marine later has developed over the inner waters and is now making its way over some of the coastal areas of San Diego County. This will continue to fill in throughout the night but likely struggle to make it into the Inland Empire. Models appear to remain on track with a strengthening ridge over the area towards the middle of the week, which will translate to temperatures being above average by Wednesday. Thursday is still looking to be the hottest day of the week. There will likely need to be heat advisories and warnings issued for the deserts and possibly the inland areas, and this could continue through Saturday until the ridge begins to weaken slightly going into the following weekend. Ensembles do show some promising signals that there could be more troughing influencing the area and possibly cooling us off going into the early part of next week, although this is still a little too far out at this time to be considered reliable. (Previous discussion submitted at 140 PM): Afternoon satellite shows low clouds offshore with smoke aloft from the Gifford Fire near San Luis Obispo. Hazy skies will continue through at least tomorrow as the fire burns. The marine layer may be slightly thinner this evening, where low clouds will stay closer to the coast and western valleys. Patchy fog will occur once again for elevated terrain into some valleys by dawn. High pressure stays anchored over El Paso, TX through Tuesday, which will lead to little change in temperatures. By Wednesday through Friday, high pressure over New Mexico will amplify and expand westward. This will bring greater warming to the region as 850mb climb near 30C. Models depict the greatest warming to be on Thursday as the high peaks in strength. The low deserts will see moderate to high (40-80%) chances to see highs exceed 115 degrees. Chances are about the same for the Inland Empire and high deserts to reach 100 degrees, along with some inland valleys of San Diego County. This will create moderate HeatRisk conditions for inland valleys and mountain areas, and high HeatRisk for the lower deserts. If you must be outside, make sure to take breaks, drink plenty of water, and find areas of air conditioning to stay cool. Slight increases in PWAT`s are seen by this period as well, but any chance of monsoonal thunderstorms continues to be below 10 percent for the mountains and deserts. Cluster analysis shows some members showing a weakening high over the Southwest, as a trough to the north introduces some lowering heights and cooler air. If this occurs, greater onshore flow and cooling would occur across the region, lowering temperatures to where they are today near average. The high may take a bit longer to weaken into the weekend though, which could delay the cooler weather pattern by a day or two. && .AVIATION... 040330Z....Coasts/Western Valleys... Low clouds based 900-1300ft MSL have been redeveloping over the waters and the immediate coast this evening. These clouds will continue to build in coverage and spread inland to about 15 miles by 09z Monday. VIS reduced to 1-5SM over higher coastal terrain and elevated western valleys. Clouds clear back through the coast by 15-17z Monday morning. Patches of smoke aloft (~10000-15000ft MSL) continues to steam in from the Gifford Fire to our distant northwest, likely persisting through Monday. No surface VIS issues from smoke are expected. .Inland Valleys/Mountains/Deserts...VFR conditions prevail through Monday evening. Patches of smoke aloft (~10000-15000ft MSL) continues to steam in from the Gifford Fire to our distant northwest, likely persisting through Monday. No surface VIS issues from smoke are expected. && .MARINE... No hazardous marine conditions are expected through 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. && $$ UPDATE...Stewey PUBLIC...APR AVIATION/MARINE...Munyan