FXUS66 KMTR 291710
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
910 AM PST Mon Dec 29 2025
...New AVIATION...
.KEY MESSAGES...
Updated at 852 AM PST Mon Dec 29 2025
- Cold overnight conditions for interior and valley locations again
tonight.
- Rain returns Wednesday and lasts through the weekend.
- Coastal flooding from King Tides is expected Wednesday through
Sunday.
&&
.UPDATE...
Issued at 852 AM PST Mon Dec 29 2025
Temperatures are gradually warming with mostly sunny skies
anticpated throughout the day. Therefore, the Cold Weather
Advisory will be allowed to expire at 9 AM PST. We will have to
monitor for a Cold Weather Advisory again tonight, yet
temperatures are currently anticipated to be a bit warmer than
this morning. Otherwise, no changes to the ongoing forecast.
RGass
&&
.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...
(18Z TAFS)
Issued at 910 AM PST Mon Dec 29 2025
High confidence in VFR through the TAF period with the exception of
STS which can expect radiation fog again tomorrow morning. Winds
will generally follow a pattern of drainage flow overnight and
northeasterly winds during the day. Tule fog is not expected to
impact any terminals directly, but expect it to creep into the area
from the Central Valley through the Delta and Altamont Pass.
Vicinity of SFO...High confidence in VFR through the TAF period.
Winds are currently more southeasterly than any guidance/models
suggest, but they should back through the TAF period to become
easterly this afternoon and then northeasterly tonight.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...High confidence in VFR through the TAF
period. Drainage winds will continue through the morning with
northeasterly winds expected this afternoon.
&&
.MARINE...
(Today through Saturday)
Issued at 852 AM PST Mon Dec 29 2025
Moderate northerly winds and moderate seas will prevail through
Wednesday. Fresh to strong southerly breezes return Thursday into
Friday with gale force gusts likely. Seas build to become rough
Thursday into Friday. Rain returns Wednesday and lasts through the
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.
PZ...None.
&&
$$
SHORT TERM...KR
LONG TERM....KR
AVIATION...Sarment
MARINE...Sarment
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Prepared by Boulder-Creek.com Weather at: Mon Dec 29 10:30:02 PST 2025
From the National Weather Service
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