Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
722 FXUS66 KSGX 132113 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 113 PM PST Sat Dec 13 2025 .SYNOPSIS... High pressure will continue to dominate the region over the next week, keeping high temperatures well above normal with minor day to day changes. The marine layer remains very shallow, leading to low clouds and fog near the coast, where the fog may be locally dense over the next couple of nights/mornings. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Today into Sunday... Satellite imagery and 500mb analysis reveal the upper level ridge which has been in control across the region extending from Baja northward into the western Great Basin, with a shortwave off the north-central California Coast. The strong and shallow subsidence inversion resulting from the presence of the ridge is keeping the marine layer very low, with fog from this morning finally clearing across most of the coastal areas this afternoon. As the shortwaves continues to round the northern side of the ridge, the ridge will weaken some and its axis will nudge eastward, leading to a slightly weaker inversion. While a similar marine layer presence is expected tonight compared to this morning, bases may be a touch higher with locally dense fog expected for higher coastal terrain through portions of the western inland valleys. Temperatures continue to stay above normal under the ridge, with very mild nighttime temperatures for elevations within the inversion (generally 2000- 4000ft). Monday and Tuesday... The shortwave trough will tighten the surface offshore gradient some for Monday afternoon, with weak offshore winds expected, primarily restricted to the main mountain passes. Strongest wind gusts of 25- 30 mph possible in these areas. The weak offshore flow will also help clear the marine layer out earlier Monday morning and allow temperatures to warm back up to 15-20 degrees above normal. Onshore flow resumes Tuesday but a meager marine layer Tuesday morning keeps afternoon temperatures similarly above normal as Monday`s. Wednesday through Late Week... Ensemble clusters continue to favor a generally zonal upper level flow with broad ridging in place through some clusters feature slightly stronger ridging. Regardless, this pattern will keep temperatures slightly above normal, albeit less anomalous than Monday/Tuesday...with no precipitation chances in sight. Higher elevations, particularly the High Deserts could see elevated onshore flow if the ridging isn`t as strong. && .AVIATION... 132100Z...Coast/Valleys...Low clouds and fog have finally moved off of the coastal sites with some scattered to few low clouds lingering around 800-900 ft MSL. Low clouds and fog are expected to return this evening after 02-03Z along the coast and up to 15 SM inland with low cloud bases around 100-500 ft MSL and visibilities 4 SM or less. Mountains/Deserts...Clear skies and VFR conditions expected through the TAF period. && .MARINE... Much patchier and not nearly as dense fog is expected to develop this evening out over the local waters and last into Sunday morning. Otherwise, no hazardous marine conditions are expected through Thursday. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ PUBLIC...Munyan AVIATION/MARINE...Villafane