943 FXUS66 KSGX 222035 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 135 PM PDT Sun Jun 22 2025 .SYNOPSIS... Minimal day to day fluctuations in temperatures through Tuesday. A gradual warming trend is expected for the middle to end of the week. The marine layer will bring night and morning low clouds to coastal areas through the week. Low clouds are expected to reach into the valleys at times, most likely during the first half of the week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Mostly clear skies are being observed on visible satellite across the region this afternoon. Marine layer low clouds and fog will eventually redevelop late tonight, reaching into portions of the valleys by Monday morning. Temperatures at 1 PM were running warmer than yesterday for most locations. Most locations west of the mountains are a few to up to 10 degrees warmer, with a few local areas mainly on mountain foothills up to 15 degrees warmer. The deserts are running a few degrees cooler than this time yesterday. A long wave troughing pattern will remain over the Western United States early this week. That will keep high temperatures 5 to 10 degrees below average through Tuesday. Marine layer low clouds and fog are expected each night and morning and will reach into the valleys. On Wednesday the upper level troughing will shift east, but cyclonic flow aloft will remain over the region into Friday. Ensembles are in generally good agreement with upper level high pressure beginning to build in from the southeast into next weekend but there remains uncertainty in the placement of the ridge. Only about 25 percent of solutions have the ridge axis over the West Coast, which would result in the hottest conditions. Regardless, a gradual warming can be expected for the middle to end of the week with lingering uncertainty in just how hot it will get. Friday through Sunday, the difference between the coolest high temperature solution and the warmest is about 10 degrees for the valleys and mountains. NBM chances of the deserts reaching or exceeding 110 degrees is around 15 percent Saturday and closer to 30 percent Sunday. The building high pressure aloft should keep the marine layer shallower and more confined to coastal areas. && .AVIATION... 222130....Coast/Valleys/Coastal Mountain Slopes...VFR conditions throughout the region this afternoon. Low clouds based 1500-2500 feet MSL redevelop across San Diego County coastal and inland areas, 08-11z Monday, then eventually Orange County 11-13z. Patchy low clouds develop along terrain surrounding the Inland Empire, similar to the last few mornings, though only small (20% chance) for MVFR CIGs at KONT or KSBD. VIS 1-5 SM where clouds intersect with terrain. Low clouds clear to the coast 15-17z Monday morning. .Mountains/Deserts...Clear skies and largely unrestricted VIS through Monday afternoon. Gusts near 20 kts possible again later this afternoon/evening in the Coachella Valley with the sea breeze push. && .MARINE... No hazardous marine conditions are 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 AVIATION/MARINE...Westerink