FXUS66 KMTR 071150 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 350 AM PST Wed Jan 7 2026 ...New AVIATION... .KEY MESSAGES... Updated at 247 AM PST Wed Jan 7 2026 - High and dry pattern through the week with offshore flow and cold overnight conditions - Hazardous beach conditions at all Pacific Coast beaches Thursday and Friday and again early next week && .SHORT TERM... Issued at 247 AM PST Wed Jan 7 2026 (Today and tonight) Flooding continues for areas near and downstream of Mark West Creek near Mirabel Heights as indicated by gauges and cameras. A Flood Warning is in effect until 8 AM - this will likely be replaced by a long duration Flood Advisory then as that is when it is forecast to recede into minor flood stage. Residual troughiness will allow for a dying cold front to skirt the region today. High clouds from this feature will continue to stream into the region which will help limit the extent of fog and stratus this morning. Sensible weather wise, expect near normal temperatures and more gloomy conditions. && .LONG TERM... Issued at 247 AM PST Wed Jan 7 2026 (Thursday through Tuesday) Global ensemble clusters are in agreement of some form of longwave upper-level ridging dominating our long term forecast and beyond. This will yield fair daytime conditions with cold overnight conditions. An Extreme Cold Watch has been issued for most of the area from 1 AM Friday to 9 AM Friday to cover the Thursday night period. It's a bit of a nuanced forecast though as it isn't a cold air mass bringing this along. In fact, 850 millibar temperatures are forecast to warm near 7 degrees Celsius which is near the daily mean. Some meteorological rule of thumb equates this to 45 degrees at 5,000 feet. To figure out what's going on, we need to zoom out. It is winter which means nights are long and therefore there is a lot of time for radiational cooling to occur. As the Earth cools, a shallow, stable layer develops near the surface, this is known as a temperature inversion. Quantitatively, this is when temperature increases with height, like in this case where we have ~0 degrees Celsius at the surface and ~7 degrees Celsius at 5,000 feet. You can think of it as a "cold lid". We are going to put a pin in this for now. At the surface, high pressure will nose into the California/Oregon border before ultimately building into the Great Basin. Along the California Coast, a coastal trough will develop which will facilitate offshore flow. Normally this would be a fire weather concern, but we are way past that. We are going to keep our fire weather thinking caps on though to understand why it is going to be cold in some spots and not others. Circling back to our "cold lid", offshore flow aloft will not be strong or turbulent enough to break its seal. Some locations downslope of/in the higher terrain are not in the Extreme Cold Watch as sufficient mixing will keep them relatively warmer. The coldest spots will be Interior Monterey and San Benito Counties, where below freezing temperatures are possible. The North Bay Coast and San Francisco Peninsula Coast will be moderated by the Pacific Ocean and downslope flow coming off of the adjacent terrain. The Friday night period will be cold, but not quite as cold as Thursday night. Overnight temperatures will slowly rise through the weekend to become above criteria by the start of next week. && .AVIATION... (12Z TAFS) Issued at 342 AM PST Wed Jan 7 2026 A weak passing front is bringing in a mix of clouds, some of the mid-high level, making it challenging to see developing sfc clouds. That being said mostly VFR with pockets of MVFR with lower cigs or patchy/transient fog. This will be the case through this afternoon. Another weak boundary sweeps through later tonight with stronger winds, clouds, and scattered showers. Lowest conf as of now are precip chc tonight. Therefore, focused on winds and lowering cigs to MVFR in the tafs. Vicinity of SFO...VFR/MVFR through the AM rush. VFR this afternoon with increasing winds. Did not issues an AWW, but could see isolated gusts up to 30 kts. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Borderline of MVFR to VFR today. VFR later this afternoon/evening. MVFR cigs return tonight with vcsh possible. && .MARINE... (Today through Monday) Issued at 247 AM PST Wed Jan 7 2026 A series of weak fronts will sweep through the region today and tonight bringing increasing northerly winds. Fresh to strong breezes will develop leading to hazardous conditions over the waters. Additionally, a moderate period northwest swell will arrive early Thursday and build through the day. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...High Surf Advisory from 1 AM Thursday to 10 PM PST Friday for CAZ006-505-509-530. Extreme Cold Watch from late Thursday night through Friday morning for CAZ502-506-508-510-512>518-528>530. Beach Hazards Statement from late tonight through Friday evening for CAZ529. PZ...Small Craft Advisory from 3 PM this afternoon to 3 PM PST Thursday for Mry Bay-Pigeon Pt to Pt Pinos 0-10 nm-Pt Arena to Pt Reyes 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm. Small Craft Advisory from 3 PM this afternoon to 9 PM PST Thursday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm. && $$ SHORT TERM...Sarment LONG TERM....Sarment AVIATION...MM MARINE...MM 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