FXUS66 KMTR 302204
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
204 PM PST Tue Dec 30 2025
...New SHORT TERM, LONG TERM...
.KEY MESSAGES...
Updated at 202 PM PST Tue Dec 30 2025
- Rain returns and becomes widespread for New Years Eve
- Friday is likely to be windy with strong southerly winds along
with locally heavy rainfall
- Coastal flooding from King Tides is expected Wednesday through
Sunday
- Unsettled conditions look to prevail through at least early
next week
&&
.SHORT TERM...
Issued at 202 PM PST Tue Dec 30 2025
(This evening through Wednesday)
Temperatures are struggling to warm this afternoon as low clouds
remain trapped beneath the high clouds advecting north across the
region this afternoon. As of this writing, temperatures remain in
lower-to-mid 40s in much of the North Bay and East Bay valleys.
However, coastal areas have warmed into the 60s and even lower 70s
across the Central Coast where offshore flow persists. That said,
minimum temperatures overnight are forecast to be warmer than
previous nights as increased moisture and cloud cover continue to
spread northward in advance of an approaching weather system.
By Wednesday morning much of the Central Coast will be experiencing
light to moderate rain that will then spread northward across the
Bay Area and North Bay throughout the afternoon and evening.
However, locally higher amounts are expected in the Santa Lucia and
Sierra de Salinas ranges where there is a marginal risk for
excessive rainfall on Wednesday and Thursday due to orographic lift.
Given the recent rainfall, this will lead to nuisance flooding for
poor drainage areas, urban areas, and rises on flashy
creeks/streams.
&&
.LONG TERM...
Issued at 202 PM PST Tue Dec 30 2025
(Wednesday night through next Monday)
Rain will continue on New Years Day, yet not as heavy or widespread
as Wednesday as the mid/upper level cut-off low pushes inland over
southern California.
By Friday, an atmospheric river is forecast to move across the North
Bay and then progress southward bringing additional rainfall to the
region and a 10-15% chance for thunderstorms. This is when we are
expecting the heaviest of rainfall, however the boundary does not
appear likely to stall at any given point. There is a marginal risk
for excessive rainfall on Friday across the interior Bay Area and
Central Coast. Southerly winds will also be strong and gusty on
Friday, especially ahead of and along the main frontal boundary that
is forecast to move through the Bay Area and Central Coast Friday
afternoon and evening. Gusts are currently forecast to be 45-55 mph
along the coast, in the higher terrain, and northwest to southeast
oriented valleys. Elsewhere expecting 35-45 mph gusts from late
Friday morning through the evening and potentially into early
Saturday morning.
Rainfall amounts and wind speeds will be better refined as we get
closer to the event. Unsettled conditions look to prevail into the
weekend and potentially into early next week as the pattern aloft
remains troughy.
&&
.AVIATION...
(18Z TAFS)
Issued at 930 AM PST Tue Dec 30 2025
Fog and low stratus persist in the North and East Bay valleys
through 19-20Z. Otherwise, the region is generally VFR with
extensive mid- to high-level clouds developing across the region
through the day. Gentle to moderate offshore breezes will prevail
through the day with little chance for showers through the day.
Overnight, winds will relax, and the incoming high clouds will aim
to disrupt radiative cooling and stratus development. Confidence
in the forecast for fog at STS tonight has decreased, but opted to
leave the TAF intact for now. Showers will build in from the
south on Wednesday morning and spread throughout the region
through the day.
Vicinity of SFO... Generally VFR with mid- to high level clouds
through the TAF period, with a gentle northeast breeze through the
day. Ceilings will lower Wednesday morning in advance of showers
expected to arrive late in the morning through the end of the TAF
period.
SFO Bridge Approach... Similar to SFO.
Monterey Bay Terminals... Gentle to moderate southeast breezes
developing through the day with mid- to high level cloud ceilings.
Winds will relax overnight in advance of showers arriving in the pre-
dawn hours Wednesday morning.
&&
.MARINE...
(Today through Sunday)
Issued at 921 AM PST Tue Dec 30 2025
Moderate to fresh east to northeast winds and moderate seas
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 into the early part of next week.
&&
.BEACHES...
Issued at 925 PM PST Mon Dec 29 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...RGass
LONG TERM....RGass
AVIATION...DialH
MARINE...DialH
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Prepared by Boulder-Creek.com Weather at: Tue Dec 30 14:30:02 PST 2025
From the National Weather Service
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