Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
917 FXUS66 KSGX 060311 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 811 PM PDT Sun Oct 5 2025 .SYNOPSIS... Below normal temperatures through Monday, with a gradual warming trend into the latter part of the week. Areas of night and morning low clouds and fog will continue along the coasts and parts of the valleys through midweek. Mid and high level tropical moisture moving into the region will bring a slight chance of showers late Thursday through Saturday. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Evening update: As of 8:00 PM, a few patchy clouds have developed along coastal areas. The closed low referenced in the previous discussion is detaching from the parent trough and now centered off the coast of central California. The parent trough is lifting and moving eastward meaning Southern California currently finds itself between these two weak upper lows. The 00z sounding shows a significantly more impressive low level inversion from yesterday`s sounding, giving increased confidence for much greater coverage in low clouds tonight, first into Orange and San Diego County lowlands and eventually into the Inland Empire during the early morning hours of Monday. Previous discussion, as of 1:42 PM: .SHORT TERM... Zooming out, a large scale positively tilted trough is over much of the north-central and western U.S. A shortwave can be seen developing on the west side of the trough off the north-central California coast currently. This will develop into a little closed low late today into Monday morning as it moves down to the south- central California coast, and the weak ridge over the southern U.S. moves to cover Southern California. This will result in a gradual warm up for areas inland from the immediate coast through Tuesday, starting with inland high temperatures today that will be 2-5 degrees warmer than yesterday`s. Temperatures will still be a couple of degrees below the daily average today, despite this mild warm up. A few degrees of warming each day through Tuesday will bring temperatures closer to normal. The inversion will strengthen tonight, leading to more widespread low cloud coverage overnight. Clouds that develop this evening will still initially be quite patchy, and could remain patchy to a certain extent overnight, but will be much more uniform than previous days and make it further inland, even possibly into parts of the western and southern Inland Empire. It will also be slow to clear in the mornings, lingering along the coast possibly into the early afternoon. Similar story through mid-week. The low lifts north and opens up late Tuesday into early Wednesday, but result in little change to the local area. A very large low pressure system will drop south from the Gulf of Alaska mid- to late-week, though models have come to more of a consensus that this impacts from this will remain well to our north/northwest through early Thursday. && .LONG TERM... The potential for some more interesting weather has increased a bit for late next week into the first half of the weekend, though confidence in the details is still low as the models struggle to resolve them. Moisture advected from now Tropical Storm Priscilla will enter the area starting Thursday, and ensemble mean precipitable water peaks around 1.25-1.5" Friday. Meanwhile the large low pressure system will continue southwards, though the main impacts and lift provided from this system looks to stay to our north. As a result, showers are possible for all areas Thursday through Saturday, with chances peaking Friday at 15-30%. Just over half of global ensemble members are now showing precipitation for San Diego County, with that number decreasing a bit for areas further north. Most of the members are indicating light precipitation, with the majority of the moisture above 700 mb, and the ensemble mean is around 0.20-0.40". A few outlier solutions are very wet, as they are showing better dynamics provided from the low traveling a little further south. This latter solution would also lead to better conditions for thunderstorms. Currently the National Blend of Models is indicating a 5-10% chance for thunderstorms, locally to 15% in some of the mountains. The low opens around Saturday and then pushes eastward late Saturday into Sunday, taking the moisture with it and ending precipitation chances likely by Sunday morning. This will also lead to cooling over the weekend to below normal temperatures. && .AVIATION... 060300Z....Coasts/Valleys...Low clouds near 1500-2000 ft MSL will continue to fill into areas near the coast this evening. A coastal eddy will help to push low clouds to many inland valleys overnight, including portions of the Inland Empire. There is a 75% chance of BKN cigs reaching KONT by 10Z Mon and a 40% chance of low clouds reaching KSBD by 12Z Mon. FEW-SCT conditions will return 17-19Z Mon for inland areas. Confidence increasing in BKN cigs lingering for VCTY KSAN/KCRQ into Monday afternoon, less so in Orange County. Low clouds with similar bases moving into the coast and western valleys after 02Z Tues. Mountains/Deserts...VFR conditions will continue through Mon. && .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...Westerink/CSP AVIATION/MARINE...APR