Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
875 FXUS66 KSGX 130822 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 122 AM PDT Sun Jul 13 2025 .SYNOPSIS... A little warmer inland for today and Monday. Gradual cooling back to near seasonal averages expected for the middle to the end of the week. While chances are still low and uncertainty remains, confidence is increasing for the potential of monsoonal thunderstorms over the mountains late in the week. Marine layer low clouds and patchy fog will spread across the coastal areas and into the western valleys during the nights and mornings. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... This morning...The marine layer is about the same depth as at this time yesterday and the low clouds are similar in coverage. Clearing may be a little faster today than yesterday as the marine layer inversion seems to be a little weaker. The dominant ridge will remain centered about 135 miles west southwest of San Diego through Monday. This will allow inland temperatures to rise by a few degrees above what they were the last couple of days. Temperatures in the mtns and deserts will be several degrees above seasonal averages while west of the mtns, temperatures will be near or a few degrees below seasonal averages. This is mostly due to a relatively shallow but persistent marine layer, with low clouds and patchy fog in the coastal areas and western portions of the inland valleys each night and morning. On Monday, a couple of inverted troughs in the southeast flow on the southern side of the east-west oriented ridge axis will bring some monsoonal moisture into SoCal but the threat of afternoon convection will be low because the moisture will be limited and mostly above 10,000 ft, although a stray shower or tstm can`t be ruled out altogether. For Tuesday through the end of the week, model solutions begin to diverge significantly introducing more uncertainty into the forecast but in general, the dominant high pressure ridge will be weakened and displaced eastward towards the Four Corners as a low pressure system moves inland over the Pacific Northwest. During this time, temperatures will begin to trend generally lower even as conditions become drier for Tue and Wed. For Thursday through the weekend, an increasing number of solutions across model platforms are indicating an increase in monsoonal moisture with a corresponding increase in the chances for afternoon showers and tstms, mainly in the mountains. This change in the pattern will likely continue the trend toward lower temperatures for the mtns and deserts. && .AVIATION... 130900Z....Coast/Valleys/Foothills...Low clouds based 1100-1500ft MSL have reached into western valleys and will reach up to 20 miles by 11z. 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 late Sun after 02z with bases closer to 1500ft MSL. .Mountains/Deserts...VFR conditions and unrestricted VIS through Monday. && .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...PG AVIATION/MARINE...Westerink