FXUS66 KMTR 260548
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
948 PM PST Thu Dec 25 2025

...New UPDATE...

.KEY MESSAGES...
Updated at 1211 PM PST Thu Dec 25 2025

 - Severe thunderstorms are possible through the afternoon and
   evening. Damaging wind gusts are the main threats, with
   tornadoes possible.

 - Strong southerly winds continue through Friday.

 - A flood watch remains in effect through Friday evening across
   the region. The main threat is flash flooding and landslides
   from high rain rates.

 - Dangerous beach and marine conditions continue through Friday
   across the Pacific coast and adjacent beaches.

 - Cold temperatures settle in this weekend after the storms break

&&

.UPDATE...
Issued at 943 PM PST Thu Dec 25 2025

The widespread severe weather threat is winding down across our
area. There may be some lingering urban flooding, especially in
poor drainage areas tonight into Friday morning, so continue to
take it slow out there if you have to travel. Light to moderate
rain at times remains in the forecast through tomorrow night when
one more line of scattered showers and (sub-severe) thunderstorms
is expected to move onshore across our whole area. Hope everyone
had a safe holiday out there!

&&

.SHORT TERM...
Issued at 1211 PM PST Thu Dec 25 2025
(This evening through Friday)

The active weather continues through this evening. While the 
widespread damaging winds have generally eased to a strong breeze,
there are still reports of gusts near 50 mph across the Bay Area.
The main threat today is possible severe thunderstorms. There has
been some scattered storms through the morning, particularly in 
the North Bay with small hail and an unconfirmed funnel cloud 
reported. The first organized band of showers and possible 
thunderstorms is reaching San Francisco now. This will gradually 
slide south through the afternoon. The big event today will push 
through this evening, around 4-7 PM. A short wave with a robust 
low level jet will help trigger what looks like a very organized, 
fast moving N-S oriented line of thunderstorms. The early 
thunderstorms were somewhat unexpected and we decided to launch a 
special 18Z balloon to get better ground truth on how unstable the
atmosphere actually is. The result was somewhat mixed. The 
overall CAPE was 170 J/kg, lower than some CAMs analyzed. But the 
distribution of was favorable, with most of the instability above 
the freezing level, but below 3 km. Overall the parameters were 
good for both high shear low CAPE tornados, and QLCS severe wind 
gusts. There is actually a very good signal on radar for a 
possible waterspout over the Monterey Bay at the moment, 
increasing confidence that the atmosphere can support tornadic 
activity today.

&&

.LONG TERM...
Issued at 1211 PM PST Thu Dec 25 2025
(Friday night through next Wednesday)

Starting Friday, winds and shower activity will gradually 
decrease as the low pressure system offshore opens up into a 
trough and moves into northern Oregon. The associated surface 
trough axis will move across the Bay Area Friday evening. This 
will finally flip the winds back to northerly, bringing drier, 
cooler weather for the weekend. The 1000-500 mb thickness actually
increases this weekend, with the cooling coming mainly from 
enhanced radiation during in the cloudless nights. Sunday through 
Tuesday look particularly calm, clear and cool as a 500 mb ridge 
sets in. The next troughing pattern looks probable on the 1st or 
2nd, just in time for King Tides. There's no strong signal for 
major impacts yet, but the CW3E ECCC AR Activity tool shows higher
than normal chances for atmospheric rivers through the first half
of January.

&&

.AVIATION...
(06Z TAFS)
Issued at 942 PM PST Thu Dec 25 2025

A strong cold front continues to move eastward across interior
California. Winds will gradually ease behind the front tonight 
and Friday. It's VFR except MVFR in passing showers, similar 
conditions continue Friday in a cooler and unstable air mass.

Vicinity of SFO...VFR-MVFR. A few showers tonight and Friday. 
Southerly winds tonight shifting to southwesterly Friday.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR-MVFR. A few showers tonight and Friday. 
Southeasterly to southerly winds tonight and Friday.

&&

.MARINE...
(Tonight through next Wednesday)
Issued at 935 PM PST Thu Dec 25 2025

...HAZARDOUS MARINE CONDITIONS CONTINUE INTO EARLY FRIDAY...  The
cold front continues to move eastward tonight. Additional  showers
will continue to develop in the unstable air mass late  tonight
and Friday. South to southwesterly gales will continue  tonight
before diminishing Friday. Very rough, choppy seas will  accompany
these gales and linger through the day Friday, reinforced by a
moderate westerly swell. If your vessel is not able to handle
these conditions return to port or seek protected waters as soon
as possible.

&&

.BEACHES...
Issued at 350 PM PST Thu Dec 25 2025

A Beach Hazards Statement continues for the coast through 4 AM 
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. 

A High Surf Advisory is then valid for the coast from 4 AM to 10 
PM Friday. For the High Surf Advisory: expect large breaking waves
up to 25 feet, strong rip currents and sneaker waves. Dangerous 
swimming and surfing conditions and localized beach erosion can be
expected. Sneaker waves can sweep across the shoreline without 
warning, pulling people into the sea from rocks, jetties and 
beaches. Large breaking waves can overpower swimmers resulting in 
significant physical injury and increase the risk of drowning. 

Inexperienced swimmers should remain out of the water due to
dangerous surf conditions.

Stay off of jetties, piers, rocks, and other waterside
infrastructure. Remain out of the water to avoid hazardous surf
and NEVER turn your back on the ocean. Monitor local weather,
surf and tide forecasts at www.weather.gov/mtr.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement until 4 AM PST Friday for CAZ006-505-509-
     529-530.

     Flood Watch through Friday evening for CAZ006-502>506-508>510-
     512>518-528>530.

     High Surf Advisory from 4 AM to 10 PM PST Friday for CAZ006-505-
     509-529-530.

PZ...Gale Warning until 3 AM PST Friday for Mry Bay-Pigeon Pt to Pt 
     Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 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-SF 
     Bay N of Bay Bridge.

&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...Canepa
MARINE...Canepa

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Prepared by Boulder-Creek.com Weather at: Thu Dec 25 22:30:02 PST 2025