690 FXUS66 KSGX 072026 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 126 PM PDT Mon Jul 7 2025 .SYNOPSIS... Warming conditions through the middle of the week, with the hottest days expected to be Wednesday and Thursday for inland locations. Conditions will return to near normal for the weekend into early next week. For early this week and the weekend, night and morning low clouds and fog will reach into the western valleys becoming shallower for the middle to end of the week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... An upper level low will remain centered off the coast of northern California into Tuesday. The low is expected to move inland through northern California Tuesday night into Wednesday. Three to five degrees of warming is expected for Tuesday with an additional few degrees of warming into Wednesday. The marine layer will still reach into the western valleys tonight into Tuesday morning. The marine layer will decrease to around 1500 feet in depth on Wednesday, keeping low clouds and fog more confined to coastal areas Wednesday and Thursday mornings. An area of high pressure aloft will strengthen over the southwestern United States and expand west across Southern California for Wednesday and Thursday. That will bring a notable increase in high temperatures, especially for the deserts. Highs on Wednesday and Thursday are expected to be 5 to 10 degrees above average for inland locations. High temperatures Wednesday and Thursday will range from the 70s near the coast; the upper 90s to 104 for the Inland Empire; and 114 to 118 for the lower deserts. In the mountains, highs are expected to range from in the mid-80 to upper 90s with the warmest conditions expected below 5000 ft. Widespread moderate HeatRisk is expected for the valleys and mountains, with widespread major HeatRisk in the low deserts. Make sure you`re staying hydrated, seeking shade, and avoiding strenuous activity during the hottest parts of the day if possible. High pressure aloft will remain over Southern California into early next week, but is expected to weaken. The weakening of the high will result in a gradual cooling trend for Friday into early next week. For next Sunday and Monday, NBM high temperatures for the coast and valleys will be near to around five degrees below average with the deserts around five degrees above average. The marine layer will deepen to 1500 to 2000 feet by next Sunday and Monday with night and morning coastal low clouds will extend inland to the western valleys. && .AVIATION... 072030Z....Coast...Low clouds with patchy coverage will gradually develop after 05Z with less probability and duration around KSNA. Bases will be around 700-1100 feet MSL with vis reduced to 1-5SM in BR along inland coastal areas. Scatter out Tuesday 14-16Z. Increasing clouds above 12000 feet Tuesday. Valleys/Mountains/Deserts...Clear with unrestricted VIS today and tonight. Increasing clouds above 12000 feet Tuesday. && .MARINE... NW wind gusts around 20 kts near San Clemente Island Tuesday and Wednesday afternoons and evenings. Otherwise, no hazardous marine weather is expected through Friday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Heat Advisory from 10 AM Wednesday to 8 PM PDT Thursday for Riverside County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Mountains- San Diego County Valleys. Extreme Heat Warning from 10 AM Wednesday to 8 PM PDT Thursday for Coachella Valley-San Diego County Deserts. PZ...None. && $$ PUBLIC...CO AVIATION/MARINE...MM