Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
158 FXUS66 KSGX 251617 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 917 AM PDT Wed Jun 25 2025 .SYNOPSIS... A gradual warming trend will continue through the end of the week. The peak of the heat is expected late in the weekend into early next week. The marine layer will bring night and morning low clouds to coastal areas through the rest of the week. The marine layer is expected to become shallower, with less low cloud coverage in the valleys by the end of the week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Low clouds had reached well into the coastal basin overnight and are clearing out of the valleys as of 9 AM. Low clouds are expected to clear to the coast by late this morning with the potential for periods of clear skies at the beaches again this afternoon. The marine layer is expected to decrease in depth, to 1500 to 2000 ft, Thursday into early next week. This will limit the inland extent of night and morning low cloud coverage to the coast and western valleys. Highs today for inland areas are expected to be 5 to 10 degrees warmer than Wednesday, with only a few degrees of warming near the coast. For the end of the week into the weekend, an area of high pressure from south of the border will build near the Four Corners region. This will result in a more noticeable warming for the deserts Friday through Tuesday. Temperatures on Sunday are trending slightly cooler than the past few days with chances of exceeding 110 degrees down to 40 to 70 percent. Chances of the low deserts exceeding 110 degrees are now highest on Monday and Tuesday at 60 to 80 percent. GFS ensemble precipitable water guidance is indicating that the position of the high pressure would allow for a moisture surge from the south/southeast into the low deserts over the weekend or early next week. The ECMWF ensemble guidance is notably drier. If the solutions with an increase precipitable water come to fruition, that would keep high temperature readings on the lower side of guidance. If it remains on the drier side of guidance, the hotter solutions will occur with higher likelihood of temperatures reaching or exceeding 110 degrees. Conditions are also expected to warm up west of the mountains, but an upper level weak trough lingering off the coast of Southern California is expected to keep the aforementioned high pressure from moving too far west. Chances of the Inland Empire exceeding 100 degrees are now highest Monday through Wednesday and still mostly 20 to 30 percent, locally up to 50 percent in the eastern portion of the Inland Empire. For the eastern San Diego valleys, chances for temperatures to exceed 90 degrees are 30 to 50 percent. Chances of inland Orange County exceeding 90 degrees on Sunday and Monday are closer to 10 to 20 percent. && .AVIATION... 251605....Coast/Valleys...Widespread low clouds and patchy fog (mostly in the Inland Empire) this morning are clearing from the inland edges toward the coast. Bases are around 2000 ft MSL and CIG impacts should end at TAF sites west of the mtns 17Z-19Z. A few low clouds could linger at the beaches into the afternoon, otherwise skies should be mostly clear. Low clouds with bases around 1500 ft MSL will return to coastal areas after 02z Thu and spread up to 15 miles inland by 14Z Thu, with patchy clouds and fog in the Inland Empire. CIG impacts likely at coastal TAF sites 03Z-18Z Thu. 30-40% chance of a CIG at KONT 11Z-16Z Thu and less chances at KSBD. .Mountains/Deserts...Clear skies with unrestricted VIS through Thursday morning. && .MARINE... No hazardous marine conditions are expected through Sunday. && .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...PG