FXUS66 KMTR 291217
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
417 AM PST Mon Dec 29 2025

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 126 AM PST Mon Dec 29 2025

 - Cold overnight conditions for interior and valley locations this 
   morning and again tonight. 

 - Rain returns Wednesday and lasts through the weekend.

 - Coastal flooding from King Tides is expected Wednesday through 
   Sunday.

&&

.SHORT TERM...
Issued at 126 AM PST Mon Dec 29 2025
(Today and tonight)

Quiet weather continues today as an upper level low slides from the 
Reno/Tahoe area across central California and into the Pacific. This 
can clearly be seen on the water vapor satellite channel this 
morning, while high pressure noses into northwest California. 
Offshore flow dominates the current weather pattern, keeping 
conditions dry and even warm and windy in the terrain, especially in 
the North Bay. In the lower elevations, or where temperatures 
struggled to recover in the mountains yesterday, temperatures will 
be chillier. The Cold Weather Advisory remains in effect for the 
valleys and interior locations, the exception being the interior 
North Bay mountains. The coldest conditions happened yesterday 
morning near or just after sunrise and we expect that to happen 
again today. 

Once we get past the chilly kickstart to Monday, temperatures warm 
into the 50s and low 60s across the Bay Area and into the mid 50s to 
mid 60s for the Central Coast. 

&&

.LONG TERM...
Issued at 126 AM PST Mon Dec 29 2025
(Tuesday through Sunday)

Cluster analysis in addition to the EPS and GEFS shows upper level 
ridging holding through Tuesday, leading to another quiet day. 
Guidance than clearly depicts ridging building over the 
Intermountain West. Over the Pacific, a cutoff trough deepens and 
gradually lifts north, transitioning more to an open wave feature. 
To the west of that, troughing over the Gulf of Alaska deepens and 
gradually advances westward. Wet weather looks to begin Wednesday, 
with periodic bouts of rain holding through the weekend. Both 
systems look to tap into tropical moisture, with IVTs projected to 
be around 250 kg/(ms). Given last week's storm systems, nuisance 
flooding for poor drainage and urban areas will be possible, as well 
rises on flashy creeks/streams. Given the nice weather over the next 
two days, now is a good time to check storm drains and gutters to 
make sure they're not clogged. The WPC has highlighted Santa Lucia 
Range and Sierra de Salinas in a Marginal Risk for excessive 
rainfall and flash flooding for Wednesday. They also placed the Bay 
Area and the Central Coast in a Marginal Risk for excessive rainfall 
and flash flooding for Friday. Given the already saturated soils and 
the trend in ensemble guidance and QPF cluster analysis, this 
appears reasonable. In addition to rain, confidence is increasing 
for gusty southerly winds for at least the Wednesday round of rain. 
Ensembles have upped the winds as we've gotten closer in time and 
the deterministic models continue to paint a 50kt+ jet at the 950mb 
level. If trends continue, a Wind Advisory may be needed. 

&&

.AVIATION...
(12Z TAFS)
Issued at 411 AM PST Mon Dec 29 2025

Offshore winds and VFR prevail through the TAF period, with the
exception of interior Sonoma county where LIFR FG is anticipated
during the morning hours. Additionally, Tule fog from the Central
Valley will also be creeping into extreme eastern Contra Costa
county during the mornings. No other concerns elsewhere.

Vicinity of SFO...VFR. Light easterly winds under a weak offshore
flow regime will persist through much of the period.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR. Light easterly winds under a weak offshore
flow regime will persist through much of the period. Exception
being invof the Salinas Valley (KSNS) where 10-15 kts of SE
drainage flow persists.

&&

.MARINE...
(Today through Saturday)
Issued at 411 AM PST Mon Dec 29 2025

Gentle northerly breeze will continue today, turning more easterly
by late tonight and through the middle of the week. Winds become
southerly and rain chances increase late Wednesday into Thursday
as the next storm system enters the waters. Seas and winds largely
remain favorable throughout the week, potentially becoming
hazardous by this weekend.

&&

.BEACHES...
Issued at 945 AM PST Sun Dec 28 2025

Perigean spring tides (king tides) return Wednesday - Sunday. 
This is due to the combination of the full moon on 1/3, lunar 
perigee on 1/1, and perihelion on 1/3. In other words all three 
planetary bodies are lined up and close to each other. In addition
to the high astronomical tide, the incoming low pressure system 
will bring strong onshore winds, generating some storm surge. The 
combination of these factors will bring minor coastal flooding to 
the low-lying areas near shorelines and tidal waterways during 
high tide Wednesday through Sunday. At the San Francisco tidal 
gauge, high tide is expected to be 1.5 ft above normal at 7:51 AM 
Wednesday, 1.7 ft above normal at 8:41 AM Thursday, 1.8 ft above 
normal at 9:34 AM Friday, 1.8 ft above normal at 10:26 AM 
Saturday, and 1.6 ft above normal at 11:18 AM Sunday. These 
predictions include 0.5 feet of storm surge that will enhance the 
astronomical tide and flooding threat. High tide varies up to 90 
minutes earlier or later along the Pacific Coast and through the 
San Francisco Bay, respectively.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory from 5 AM Wednesday to 2 PM PST Sunday 
     for CAZ006-505-506-508-509-529-530.

     Cold Weather Advisory until 9 AM PST this morning for CAZ506-510-
     513>518-528.

PZ...None.
&&

$$

SHORT TERM...KR
LONG TERM....KR
AVIATION...Behringer
MARINE...Behringer

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Prepared by Boulder-Creek.com Weather at: Mon Dec 29 06:30:02 PST 2025