Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
225 FXUS66 KSGX 062127 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 227 PM PDT Mon Oct 6 2025 .SYNOPSIS... High pressure to the southeast will bring gradually warmer days into Wednesday. The marine layer will decrease in depth with night and morning low clouds not spreading as far into the valleys by Wednesday. Thursday into Saturday, moisture from the remnants of Hurricane Priscilla is expected to spread into the southwestern California with chances for showers peaking on Friday. Low pressure from the northwest will bring cooling for next weekend with high temperatures as much as 5 to 10 degrees below average for inland areas next Sunday. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .SHORT TERM... Afternoon high temperatures are warmer than yesterday by a degree or five as heights rise slightly locally with the intrusion of weak ridging from the east, with weak low pressure off the south- central CA coast at the west end of a broad, negatively titled trough over the northwest U.S. A gradual warming trend continues through Wednesday as the ridge continues to nudge in, bringing high temperatures to just about average by mid-week. The marine inversion will strengthen and lower slightly in the next few days, with more coastal low clouds in the late evening through mid- to late-morning each day through Wednesday night. Low clouds look to start out patchy again this evening, becoming more consistent/widespread towards 9-10 PM. Not the best possible viewing conditions for the supermoon at the immediate coast, but it will very likely be visible most coastal areas in the earlier evening before the clouds build in, with great visibility farther inland. && .LONG TERM... Remnant moisture from now Hurricane Priscilla will start to move into the area late Wednesday into Thursday morning, drawn in by southwest flow from a large low pressure system moving down the OR/northern CA coast. Ensemble model PWAT rises to just above an inch by the end of the day Thursday, then peaks around 1.5" by Friday. The average PWAT for this time of year is just under 0.75", so this is well above average. However, remaining model spread and likely a lack of strong forcing makes for a low confidence forecast. What we do have a widespread 15-20% chance for measurable (>= 0.01"), generally showery precipitation across the region as early as Thursday morning, increasing to 25-35% Thursday into Friday. Rainfall totals are still in question with model uncertainty remaining (despite better agreement today). 24 hour total probabilities of rainfall >= 0.25 are about 20% over southern and eastern portions of the area and 30% over the mountains and parts of the deserts by late Friday. Probability for >=1.00" is about 10%, locally 15%, over the SD, Riverside, and eastern SBD mountains and parts of the deserts. The majority of ensemble members show generally light precipitation for west of the mountains with a few stand out members, but there is the potential for fairly good upslope flow under the southwest winds aloft, especially for parts of the SBD mountains. Another point of uncertainty is the thunderstorm potential. Dynamics don`t look great, with minimal MUCAPE even at its peak on Saturday, but enough for a 10-15% chance for thunderstorms most over the mountains and SD desert. The northwest trough moves more fully into the region late Saturday/Sunday, effectively cutting off the moisture source and also cooling temperatures back to 5-10 degrees below average over the weekend into early next week. && .AVIATION... 061930Z....Coasts/Valleys...Intermittent patchy cigs will continue at the coast through the afternoon with bases mainly 1500-2000 ft MSL. Low clouds with bases 1200-1800 ft MSL will become more widespread 03-06Z Tue. There is a 40% chance of cigs reaching KONT 11-14Z Tue, with lesser chances for low clouds to reach KSBD. Areas of vis 3-5SM HZ in portions of the valleys and near higher coastal terrain. Low clouds will clear 17-19Z Tue with the potential for low clouds to again linger along portions of the coast into Tue afternoon. Mountains/Deserts...Mostly clear and VFR conditions into Tue. && .MARINE... No hazardous marine conditions are expected through Thursday. Friday afternoon, there is a 5-10% chance of thunderstorms within 10 nautical miles of the coast. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ PUBLIC...CSP AVIATION/MARINE...CO