Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
835 FXUS66 KSGX 130400 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 900 PM PDT Sat Jul 12 2025 .SYNOPSIS... Brief warming for Sunday and Monday. Gradual cooling back to near average for mid July expected for the middle to the end of next week. While chances are still low and uncertainty remains, some confidence is increasing for the potential of monsoonal thunderstorms over the mountains late next week. 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... Satellite at 9 PM was showing low clouds along much of the coast. The 00Z sounding from KNKX showed the marine layer depth to be around 1500 ft with low clouds expected to make it into the valleys overnight. Forecast remains on track with no changes made this evening. From previous discussion issued at 2 PM July 12... The dominant upper ridge in control of the region`s weather is currently displaced just off the California and is also a tad weaker than it was earlier in the week. The ridge restrengthens and spreads back overhead Sunday and Monday, leading to a rebound in temperatures up about 5 degrees warmer than today. The marine layer depth decreases some with the building ridge, but will still be around 1500-2000ft deep. By mid-late Monday, a shortwave trough rounding the upper ridge will be on the southern periphery, which looks to place it across northern Baja. While some monsoonal moisture will likely accompany this shortwave, any convection will likely be limited to the mountains in northern Mexico. While unlikely, a stray storm over the extreme southern San Diego County mountains cannot be ruled out. By Tuesday/Wednesday, this disturbance will have passed but should leave the ridge weakened and displaced back to the eastern Four Corners Region. This opens the door for a series of disturbances Thursday through the end of the week. While model guidance continues to show a fairly vast range of solutions in the exact placement of the ridge and corresponding tracks of the aforementioned disturbances, more ensemble members (notably out of the higher- resolution ECMWF which were previously more dry in the last several runs) are starting to coalesce around the chance of diurnal monsoonal thunderstorms in the mountains possible each afternoon Thursday-Saturday. Significant uncertainty in timing is muddling the view here and a few more days of seeing how the pattern evolves is necessary to say with much confidence who will see, or even if, thunderstorms occur. There is still good agreement in a gradual cooldown as a result of this pattern, which has many locations 5 to 10 degrees cooler on Wednesday compared to Monday. && .AVIATION... 130330Z....Coast/Valleys/Foothills...Low clouds linger just off the coast with bases 1100-1500ft MSL. Clouds will push inland over the next two hours, reaching up to 20 miles by 11z. Bases may fall a bit closer to 900-1200ft MSL after 07z with localized VIS reductions for valleys and terrain down to 3-5SM. CIG expected at KONT and much of the Inland Empire after 10z with bases closer to 700-900ft MSL. Clouds clear to the coast by 16-18z, possibly lingering at the beaches through the afternoon. Clouds develop and push in again Sunday night after 02z with bases closer to 1500ft MSL. .Mountains/Deserts...VFR conditions and unrestricted VIS through this weekend. && .MARINE... No hazardous marine conditions expected through Thursday. && .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...CO/Munyan AVIATION/MARINE...Zuber