Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
668 FXUS66 KSGX 101115 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 315 AM PST Wed Dec 10 2025 .SYNOPSIS... High temperatures will continue to warm for inland areas today, to around 20 degrees above average for portions of the inland valleys with locally gusty Santa Ana winds to 35 mph near the coastal slopes of the mountains through this morning. Cooling for the coast and valleys on Thursday and Friday will spread inland over the weekend as high pressure aloft weakens and weak onshore lower-level flow returns. A shallow marine layer will return for Thursday and Friday with night and morning coastal low clouds spreading locally into the western valleys over the weekend as the marine layer slowly deepens. High temperatures will be coolest on Sunday and Monday, but still 10 to 15 degrees above average for inland areas. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .SHORT TERM (Today through Friday)... High temperatures for inland areas will continue to warm today, to around 20 degrees above average for portions of the inland valleys and lower coastal mountain slopes, while coastal areas cool a few degrees. High temperatures for today will range from the lower to mid 70s near the coast to the 80s for the valleys with the lower to mid 80s for the lower deserts. Northeast winds along and below the coastal slopes of the mountains into this morning will locally gust to 35 mph. Greater cooling of a few to around 5 degrees will spread into the coast and valleys on Thursday as weak onshore flow and a shallow marine layer returns. High temperatures on Friday will be a few degrees cooler for the coast and valleys with not much change for the deserts. High temperatures on Friday will range from the mid to upper 60s near the coast to the mid 70s to lower 80s for the valleys with the lower to mid 80s for the lower deserts. Some patchy low clouds and locally dense fog could return near the coast Thursday night into Friday morning with a more likely return along with increasing coverage of low clouds and fog for Friday night into Saturday morning. && .LONG TERM (Saturday through Tuesday)... Slow cooling will continue to spread inland for Saturday and Sunday with not much change on Monday as weak onshore flow continues and the marine layer slowly deepens. Night and morning coastal low clouds will increase in coverage over the weekend and may locally extend inland into the far western valleys. Even with the cooling, high temperatures for inland areas on Sunday and Monday will still be around 10 to 15 degrees above average for inland areas, ranging from the mid to upper 60s near the coast to the mid to upper 70s for the inland valleys with the lower deserts around 80. For the middle and latter part of next week, the calibrated deterministic NBM continues to show slowly warming high temperatures, but with increasing spread in the high temperature guidance due to increasing spread in the strength of high pressure aloft along the West Coast. For Ontario, the spread between the 25th and 75th percentile of the high temperature guidance increases from as little as two degrees for today through Friday of this week, to 10 degrees for Thursday and Friday of next week. && .AVIATION... 101030Z...Clear and VFR conditions will continue today and tonight. Areas of northeast winds gusting 25-30 kts in the foothills and locally into adjacent valleys through 22Z. && .MARINE...Patchy, intermittent fog could reduce local visibility below 1 NM at times early Thursday morning through Friday morning. Otherwise, no hazardous marine conditions are anticipated 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...17 AVIATION/MARINE...MM