771 FXUS66 KSGX 301826 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 1026 AM PST Tue Dec 30 2025 .SYNOPSIS... Cloudy and warm today today with periods of very light rain or sowers, not enough to wet the ground. Santa Ana winds remain gusty this morning, then weaken by this evening across the mountains and western valleys. A low pressure system will bring periods of showers for New Year's Eve and New Year's Day with the potential for more cloudier and wet weather by the end of the week into early next week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... This morning...Sfc pressure gradients remain strongly offshore, with northeast to east winds gusting 35-45 mph in the wind-prone areas. The offshore winds at the surface will weaken during the day today, becoming light tonight. A very dry layer of the atmosphere extends upward from the sfc to about 12,000 ft. Above that, widespread clouds in a deep, moist layer are moving from south to north in a warm advection process on the eastern side of an upper level low about 650 miles southwest of San Diego. These mid to high level clouds are producing light rain/showers but a percentage of the precip is evaporating in the dry sub-cloud layer. As a result, the precip reaching the surface is likely not enough to make the roads wet except possibly at higher elevations where the dry layer is not as deep. This pattern has also produced generally warmer conditions at the sfc and temperatures are as much as 11-12 degrees higher in the coastal areas than at this time yesterday, as much as 15-20 degrees higher in the inland valleys, as much as 10-15 degrees higher in the mtns and a few degrees higher in the deserts. This warm overrunning pattern will continue through Wednesday as the low to the southwest moves northeast. The deep, moist layer aloft will gradually extend lower in the atmosphere and over time, more rain is likely to reach the ground but still not enough to produce significant impacts. Temperatures on Wed will be lower but will remain near or slightly above seasonal averages. For Wed evening through Thu...This is the period of time when most of the rainfall will occur as the closed low to the southwest accelerates to the northeast and becomes an open wave. It will produce enough dynamic forcing for deep convection, resulting in periods of heavier showers which will be more efficient at extracting moisture from the atmosphere. Rainfall rates during heavier showers will likely range from 0.3"-0.5" per hour, with about a 50% chance of exceeding 0.5" per hour. The greatest accumulations will be in the San Bernardino Mountains and on the coastal slopes where totals will range from about 1.5" east of the Cajon Pass to about 4.5" near the LA County line. Elsewhere, rainfall amounts will range from 1"-1.3" in the coastal areas, 0.9"-1.25" in the inland valleys, 1.1"-1.8" in the San Diego and Riverside County mtns, 0.15"-0.75" in the low deserts, and 0.25"-0.9" in the high desert. There will be a break from the precip on Fri as a weak dynamic ridge builds between the (now) trough moving east and a low pressure system moving southeast out of the Gulf of AK. Temps will rise slightly, especially in the low deserts where temps could climb back into the 70s. The low from the Gulf of AK will resume the precip for Sat-Sun. This system will bring colder air but will have less available moisture. Temps on Sat and Sun will be in the 60s west of the mtns and precip amounts will range from a trace to 0.25" in the San Diego and Riverside County mtns as well as areas west of the mtns. The deserts will be lucky to get any measurable precip and the San Bernardino Mountains will likely get about 0.2"-0.8"...greatest west of the Cajon Pass. A reinforcing major shortwave trough moving into the base of the existing trough over the west coast will continue the unsettled weather and bring chances for additional precip for Monday and Tuesday. Most precip will fall in the San Bernardino Mountains where Mon-Tue totals will range from about 0.2" east of the Cajon Pass to about 0.7" west of the Cajon Pass. Elsewhere, amounts will range from a trace to 0.25", except the low deserts which may get no measurable precip. Snow levels will likely remain above 8,000 ft through Friday before dropping down to about 6,500-7,500 ft for Sat through next Tue. Snowfall estimates near resort levels are for a trace to about 4 inches between Sat and next Tue. && .AVIATION... 301600Z...Generally VFR conditions through the TAF period with increasing coverage of BKN-OVC high clouds AOA 10,000ft. Intermittent very light -RA/-SHRA moving northwards today and tonight, but is unlikely to cause any cig/vis impacts. Gusty offshore winds have largely relaxed across the region, with localized gusts near 20-30 kts possible in the mountain passes and coastal slopes through late this afternoon before offshore winds diminish this afternoon. -SHRA become more widespread and slightly heavier Wed morning, with intermittent reduced vis 5-6 SM and widespread clouds closer to 5,000ft MSL. RA chances increase and spread substantially Wednesday evening. && .MARINE... Strong southerly winds develop by mid day Wednesday, prevailing into Thursday afternoon, with gusts up to 20-25 knots at times. Winds calm late Thursday afternoon, then no hazardous marine weather conditions expected through Saturday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Wind Advisory until 1 PM PST this afternoon for San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Mountains-San Diego County Valleys-San Gorgonio Pass near Banning-Santa Ana Mountains and Foothills. PZ...None. && $$ PUBLIC...PG AVIATION/MARINE...CSP