030 FXUS66 KSGX 310402 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 802 PM PST Tue Dec 30 2025 .SYNOPSIS... Mild tonight with thick high cloud cover and a few sprinkles at times. Breezy east winds continuing along the coastal slopes and foothills into Wednesday. A low pressure system will bring periods of showers for New Year's Eve and New Year's Day with the potential for more cloudy 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... Evening update... Thick high clouds are moving north over the area this evening. Breezy easterly Santa Ana winds continue across the coastal mountain slopes, foothills, and locally into the valleys. These winds have kept temperatures in the low to mid 70s across parts of the coasts and San Diego County valleys. The high cloud cover and offshore flow combination will lead to a mild night for most areas west of the mountains. There could be a few sprinkles here or there tonight, but with the extremely dry subcloud layer don't expect any of this to result in accumulating precipitation. As we get some top-down moistening towards Wednesday morning with the approaching upper level low, precipitation chances increase to around 50% though any accumulation Wednesday morning will be limited to a few hundredths of an inch. Otherwise a little cooler on Wednesday with highs around seasonal averages. Previous discussion... 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 1.9" east of the Cajon Pass to about 5" near the LA County line. Elsewhere, rainfall amounts will range from 0.9"-1.8" in the coastal areas, 0.9"-1.8" in the inland valleys, 1.1"-2.2" in the San Diego and Riverside County mtns, 0.25"-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 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... 310400Z...Generally VFR conditions tonight with BKN-OVC high clouds 8000-12000 ft. Easterly gusts near 20-30 kts in the mountain passes and coastal slopes and locally into valleys will diminish 06-09Z Wed. A lull is expected Wednesday morning before gusts 20-30kts return 18Z Wed-00Z Thu. SCT -SHRA moves in from south to north starting 12-15Z Wed with bases lowering to 5000-7000 ft MSL. Intermittent minor vis reductions (4-6SM) possible from the coast to the mtns into the afternoon hours. SHRA increases in coverage and becomes heavier starting 03-06Z Thu with bases lowering again to 2000-4000 ft MSL. Widespread MVFR cigs/vis likely with intermittent IFR cigs/vis through the overnight hours. && .MARINE... Southeasterly winds start to strengthen Wednesday afternoon, with conditions hazardous to small craft Wednesday evening through Thursday afternoon, bringing south to southeast gusts to 25 knots. Winds turn westerly before diminishing 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...Flood Watch from Wednesday evening through Thursday evening for Orange County Coastal Areas-Orange County Inland Areas-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-Santa Ana Mountains and Foothills. PZ...Small Craft Advisory from 7 PM Wednesday to 3 PM PST Thursday for Coastal Waters from San Mateo Point to the Mexican Border and out to 10 nm-Waters from San Mateo Point to the Mexican Border Extending 10 to 60 nm out including San Clemente Island. && $$ PUBLIC...SS AVIATION/MARINE...KW