256 FXUS66 KSGX 111545 AFDSGXArea Forecast Discussion National Weather Service San Diego CA 845 AM PDT Thu Sep 11 2025
.SYNOPSIS... Gradual warming trend expected into the middle of next week. Night and morning low clouds and fog will be present each day into early next week along the coast and into portions of the valleys. Some monsoonal moisture may return for the middle and latter part of next week.
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.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...
As the upper level low pressure system continues to move east, reaching the Rockies by Saturday. In the absence of the low, an upper level ridge of high pressure will briefly build over the West Coast Saturday. As a result, a gradual warming trend will occur for the end of this week into the weekend. Even with the warming, high temperatures will remain below average through Sunday.
On Sunday an area of low pressure will develop and linger off the Southern California coast and push the ridge east. Due to the southerly position of the low, the air mass will be on the warmer side. That will support the continuation of a gradual warming each day into the middle of next week. By Tuesday some valley locations are expected to experience above average temperatures with more widespread above average temperatures west of the mountains on Wednesday and Thursday. The mountains and deserts are expected to remain near or slightly below average for this time of year. Temperatures in the mountains and deserts will be moderated by an influx of monsoonal moisture for the middle to end of next week. The moisture looks to peak on Friday. NBM daily chances for measurable rainfall for Big Bear increasing to 10 percent on Wednesday, 19 percent on Thursday, and 25 percent on Friday.
A marine layer near 3000 feet deep today will gradually decrease in depth for Friday and Saturday. Coastal low clouds will extend into portions of the inland valleys for late tonight into Friday morning, and into the western valleys for late Friday night into Saturday morning. For next week, the marine layer will become shallower with night and morning coastal low clouds extending into the far western valleys at times late each night.
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.AVIATION... 111515Z...Coast/Valleys...Ceilings varying between 2000-3000 ft MSL this morning in the coastal basin with a few clouds around 1000- 1,500 ft MSL. Ceilings will be patchy and intermittent, slowly clearing by 19z. Low cloud bases around 1800-2500 ft MSL will begin to reform in western San Diego County around 23-01Z, and then fill into Orange County and the inland areas after 04Z. Full cloud coverage of the coastal basin is not expected.
Mountains/Deserts...VFR conditions prevail today and tonight. Breezy Westerly winds of 20-25 kts with gusts up to 40 kts 21-10Z today through Friday morning in the mountain passes and into adjacent deserts, causing isolated pockets of LLWS and up/downdrafts in lee of mountains.
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.MARINE... No hazardous marine conditions are expected through Monday.
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.SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions.
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.SGX WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None.
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PUBLIC...CO AVIATION/MARINE...Villafane
NWS SGX Office Area Forecast Discussion