Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
781 FXUS66 KSGX 120847 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 147 AM PDT Sat Jul 12 2025 .SYNOPSIS... Slightly cooler conditions today followed by a slight rebound in temperatures for Sunday and Monday. Gradual cooling back to near average for mid July expected for the middle to the end of next week, with perhaps some monsoonal moisture spreading into the region. Night and morning low clouds will spread across the coastal areas and into the western valleys late each night. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... This morning, the large upper level high pressure ridge remains centered roughly over the Southern California Bight. This is keeping the marine layer at a depth of nearly 2000 ft. Low clouds have spread up to about 15 miles inland and could spread farther inland by sunrise. Inland temperatures have been several degrees above seasonal averages while the coastal areas and western portions of the inland valleys have been several degrees below seasonal averages. The dominant high pressure ridge will remain roughly in place through early next week but will be somewhat weakened on Monday and Tuesday by a low-pressure trough to the northwest and a couple of inverted troughs moving in from the east with southeast flow in the mid levels. The mid level flow will likely bring some monsoonal moisture into extreme southwestern CA on Monday. There may be enough moisture and instability for convection on Monday afternoon but the probability of occurrence looks very low at this time. By Tuesday, the high aloft will shift south and east in response to a low/trough moving inland to the north. This will likely displace the moisture south and east away from SoCal. The evolution of this high pressure ridge will keep inland temperatures several degrees above seasonal averages. Daytime high temperatures in the lower deserts are expected to remain in the 106-112 degree range. The high deserts will remain in the 90s to about 105 while portions of the Inland Empire will be in the mid to upper 90s. With respect to the synoptic pattern, numerical guidance across model platforms is consistent through Tuesday although some spread in the details remains. Beyond Tuesday, model guidance is less consistent and the spread among solutions is greater, leading to less confidence in the details of the forecast. The most likely scenario is for the high pressure ridge to weaken and be displaced south and east as a trough of low pressure moves in from the northwest. This will bring general cooling and a slightly deeper marine layer. Inland temperatures for Wed through the end of the work-week will be near or a few degrees above seasonal averages, even in the lower deserts where daytime high temperatures will be in the 102-108 degree range. There are indications of a return of some monsoonal moisture for Thursday into next weekend but the probability of convection is difficult to determine at this point. && .AVIATION... 120900Z....Coast/Valleys...BKN-OVC low clouds 1200-1500 ft MSL have moved to inland areas, ultimately extending to around 15 miles inland with high terrain obscured in clouds/fog. Increasing chance for more clearing toward the coast 18-20Z Saturday with TAF sites clearing 17- 19Z. Clouds will regather tomorrow evening around 01-02Z and fill back in tomorrow evening, with very little deviation in cloud base heights from where they are this evening. Mountains/Deserts...VFR conditions and unrestricted VIS through this weekend. && .MARINE... No hazardous marine conditions expected through the middle of next week. && .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...Westerink