FXUS66 KMTR 241218 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 418 AM PST Wed Dec 24 2025 ...New UPDATE... .KEY MESSAGES... Updated at 208 AM PST Wed Dec 24 2025 - Hazardous and damaging winds continue through the morning, with a lull during the day before strong winds resume tonight through Thursday. - Flood Watch remains in effect through Friday evening across the region. The main threat is flash flooding from high rain rates. - Slight chances for severe thunderstorms continue through Thursday with thunderstorm risks continuing through Friday. Severe threats include damaging wind gusts and possible tornadoes. - Dangerous beach and marine conditions continue through Friday across the Pacific coast and adjacent beaches. - Cold temperatures settle in behind the storm systems for the weekend into the beginning of next week. && .UPDATE... Issued at 416 AM PST Wed Dec 24 2025 Main frontal band continues to move through the East Bay, South Bay, and Monterey Bay regions. Several reports of roadway flooding have been received from across the region. All wind products have been extended through 8 AM today, with high confidence of new wind products issued for tonight and Thursday afterward. Otherwise forecast remains the same. Operations team continues to be in warning operations. DialH && .SHORT TERM... Issued at 208 AM PST Wed Dec 24 2025 (Today and tonight) The strong winds, offshore thunderstorms, and scattered reports of flooding through the night so far can all be traced to a cyclonic system off the North Coast, moving parallel to the West Coast as it crosses into the waters off Oregon. The associated frontal band is moving across the coastal waters, with thunderstorms along the narrow cold-frontal rain band prompting the issuance of Special Marine Warnings. On land, the strongest gusts reported so far tonight were 95 mph at the Pine Mountain Fire Road PG&E station in the highlands of marin County, 93 mph at the Lone Tree Towers PG&E station in the very northeastern corner of San Benito County, and 89 mph at the Oak Ridge RAWS in northwestern Sonoma County. The strong winds will continue through the next few hours with the winds decreasing rapidly once the front moves through the region. A High Wind Warning is out for the coastal regions, and a Wind Advisory for the interior, until 4 AM this morning. There is also a slight, but non-zero, chance for severe thunderstorms across much of the region today, with the SPC outlook showing a Marginal risk for severe thunderstorms across the coastal region and inland into the Salinas Valley, the area towards the west of the Diablo Range, and the Sonoma County valleys. The severe weather chances remain elevated through the pre-dawn hours this morning as strong ascent and a robust coastal jet will enable severe winds to mix to the surface within the strongest convection, resulting in damaging wind gusts. In addition, the special 6Z sounding from Oakland does show a little bit of directional shear near the surface, meaning that any cell able to tap into this helicity could spin up a brief tornado. Finally, the system continues to bring chances for heavy rainfall, generally within the convective cells that develop through the morning hours. The Flood Watch remains in effect through Friday, but the outlook has transitioned from a multi-day period of steady, intense rain resulting in river flooding concerns, to an elevated risk of flash flooding across the region. As the front moves through the region, the rain should diminish, winds should die down, and the chances for convection decrease for the rest of the day. This might be a good time to take stock and make any quick repairs or other necessary actions. Emphasis on the word "quick" though. Behind this system, another low pressure system will develop in the eastern Pacific and approach the West Coast. This will bring us a second round of strong winds, heavy rainfall, and convective chances for tonight through Thursday morning. It's likely that a new set of High Wind products will be issued for this coming storm period once the products currently in effect expire. In a mostly academic concern, high temperatures today will range from the middle 50s to the lower 60s across the lower elevations, into the upper 40s to the lower 50s in the higher elevations. && .LONG TERM... Issued at 208 AM PST Wed Dec 24 2025 (Thursday through Tuesday) Strong winds and periods of heavy rain will persist into Thursday (Christmas Day) and Friday as the low pressure system meanders off the North Coast, and the Marginal risk for severe thunderstorms continues for the Central Coast through the day, with severe wind gusts and brief tornadoes being the main threats. The extended period of more moderate and heavy rain across the region will result in increased flooding concerns, especially within urban areas with rises in small creeks and streams and mainstem rivers likely, particularly within the North Bay where more antecedent rainfall has fallen. The return of the strong winds coupled with the more saturated soils will also increase the risk for additional power outages and downed trees into Friday. Make sure you have multiple ways to receive warnings through Friday in case severe thunderstorms develop. This is especially important as the increased risk for power outages could mean that some communication systems could be impacted, especially in rural and remote regions. Later on Friday, the low pressure system will degrade into a trough as it approaches the California coast, with lingering showers continuing into Saturday morning. Behind the parade of systems, cold temperatures will develop for the weekend into the early part of next week, with low temperatures dropping into the middle to upper 30s across the inland valleys. Meanwhile, the storm door remains open with long range guidance suggesting the potential for additional systems through the early portion of January. && .AVIATION... (12Z TAFS) Issued at 355 AM PST Wed Dec 24 2025 The main rain band, which offers the strongest winds and heaviest rains is exiting the area and pushing east. Conditions improve through the morning into the early afternoon before deteriorating again in the evening as showers and storms arrive across the region. This is a high confidence event in terms of occurrence, but moderate confidence in timing. Chance for thunderstorms exists at all terminals through this TAF period. However, confidence only high enough to include later in the period. TS hazards include downbursts and isolated occurrences of waterspouts. Additional concerns will be with LLWS with many TAF sites seeing winds aloft 30 kts stronger than the prevailing surface winds into early Thursday. Vicinity of SFO...Strong winds linger into the mid morning with lingering shower activity. Winds stay breezy until the late morning, but rebuild in the afternoon as spotty showers and storms approach the area. Thunderstorm chances increase into the evening, as well as winds and gusts. Storm chances and winds reduce into the night, but rebuild again into early Thursday. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Main band of rain is passing through the Monterey Bay and will exit to the east. Winds reduce in it's wake, with VFR conditions expected. Lingering shower chances reduce into the afternoon but winds and storm chances rebuild in the late afternoon and early evening. Winds and storm chances see a brief decrease into the night, but stronger winds and increase storm chances are expected into early Thursday && .MARINE... (Today through Monday) Issued at 355 AM PST Wed Dec 24 2025 ...HAZARDOUS MARINE CONDITIONS CONTINUE INTO EARLY FRIDAY... Gale- force winds are affecting the waters with the inner waters still seeing storm- force winds. These winds are building very rough, steep waves with a significant wave height near 20 feet. Showers and storms will move through the waters into the mid to late morning. Additional showers and storm chances arrive into the evening. Another gale- force low is anticipated to enter the waters early Thursday morning. If your vessel is not able to handle these conditions return to port or seek protected waters as soon as possible. && .BEACHES... Issued at 355 AM PST Wed Dec 24 2025 The strong winds along the coast will result in hazardous beach conditions. A Beach Hazards Statement has been issued for the coast through 4AM Friday. The main concerns include:blowing and drifting sand and wind waves up to 20 ft. The drifting sand and increased sea spray will also result in poor visibilities, affecting water rescues. Increased coastal erosion will be possible as well. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...High Wind Warning until 8 AM PST this morning for CAZ006-502-503- 505-509-516-517-528>530. Beach Hazards Statement through late Thursday night for CAZ006- 505-509-529-530. Flood Watch through Friday evening for CAZ006-502>506-508>510- 512>518-528>530. Wind Advisory until 8 AM PST this morning for CAZ504-506-508-510- 512>515-518. PZ...Gale Warning until 3 AM PST Friday for Mry Bay-Pigeon Pt to Pt Pinos 10-60 NM-SF Bay N of Bay Bridge. Storm Warning until 3 AM PST Friday for Pigeon Pt to Pt Pinos 0- 10 nm-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10- 60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm. && $$ SHORT TERM...DialH LONG TERM....DialH AVIATION...Murdock MARINE...Murdock Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, X, and YouTube at: www.facebook.com/nwsbayarea x.com/nwsbayarea www.youtube.com/nwsbayarea