Foster City, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

116
FXUS66 KMTR 240627
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1027 PM PST Tue Dec 23 2025

...New AVIATION...

.KEY MESSAGES...
Updated at 219 PM PST Tue Dec 23 2025

 - Make final preparations for strong winds this afternoon.
   Conditions deteriorate rapidly this evening.

 - Hazardous, damaging winds arrive this evening and continue
   into Wednesday morning. A High Wind Warning is in effect along
   the coast with a Wind Advisory across the interior.

 - Flood watch in effect across the area through Friday evening.
   The main hazard is flash flooding from high rain rates.

 - A slight chance of severe thunderstorms with strong wind gusts
   late Tuesday through Thursday with the potential to continue
   into Friday. Severe threats include damaging wind gusts and
   possible tornados.

 - Dangerous beach and marine conditions anticipated late Tuesday
   through Friday for all Pacific Coast Beaches

&&

.UPDATE...
Issued at 908 PM PST Tue Dec 23 2025

We`re in full swing of warning ops as of earlier this evening,
with no update to the forecast necessary before the scheduled
update overnight. The front edge of the first of numerous rounds
of impactful weather have begun to be felt along our entire
Pacific Coast. There have been a number of wind gust reports of
60 MPH or higher over our coastal ranges and higher elevations
farther inland. The highest so far is 75 MPH at 7 PM near North
Gonzales in Monterey County, a PG&E station at 944ft elevation.

Bottom line, this is the beginning of a very active period of
weather for our entire area through Friday. Expect power outages
and extensive travel delays. Charge all your electronics that you
rely on to receive weather warnings and alerts.

&&

.SHORT TERM...
Issued at 219 PM PST Tue Dec 23 2025
(This evening through Wednesday)

The short term threats are wind, severe thunderstorms, and
flooding, in that order. Southerly winds are picking up as a
rapidly intensifying low pressure system over the Eastern Pacific
barrels towards Northern California. The 18Z OPC analysis pegged
the central pressure at 1001 mb with an expected drop into the
980s over the next 24 hours as the system moves towards the CA/OR
border. This pressure fall will create a tight gradient with
higher pressure over the desert SW, generating sustained gale
force winds over the far Eastern Pacific and along the coast
tonight. The wind direction will gradually shift from SSE to SSW
as the low continues north. This will line up with the coastal
terrain, enhancing a southerly coastal jet. The 925mb winds look
to peak at a remarkable 70 kts right along the coast around
midnight before a front moves through and the wind speed decreases
steadily through the morning. This should translate to widespread
gusts of 60 mph along the coast, with 50 mph inland. Winds will
also be enhanced in any valleys that line up with the wind
direction. For example, the Salinas airport is already gusting to
40 kts, well ahead of the peak of the event. All indications are
that the winds will quickly subside through the morning hours
before we catch a brief break through the day Wednesday.

As the associated cold front moves through there is also a slight
chance for thunderstorms on either side of the boundary. With the
intense low level jet enhancement, any storms that form could
become severe. The main threat is damaging winds and tornados.
This is a high shear, CAPE set-up with low topped rotating storms
possible. The CAPE doesn`t break 200 J/kg, but the 0-6km shear
gets above 80 kts after the surface front moves through. A good
portion, perhaps 50% of that is in the lowest 0-1km, helping to
support tornadogenesis if any of the convection can become
surface based. SPC has expanded the marginal risk of severe
thunderstorms overnight to include the entire coast down to Pt.
Conception.

Finally this system will also bring heavy, but relatively short
duration, rainfall. The flood watch remains in effect, but it`s
less of a multi-day, widespread river flooding concern, and more
of a high rain rate flash flood concern. Fortunately the cells
will be moving very fast, so there will have to be a few in a row
to cause any real concern. By the time the sun comes up we should
just be dealing with scattered showers and limited flooding
concerns.

&&

.LONG TERM...
Issued at 210 AM PST Tue Dec 23 2025
(Wednesday through Monday)

Impacts from the initial Tuesday night to Wednesday morning system
will decrease by late morning, but, a second potentially more
impactful system will arrive late Wednesday and continue through
Friday. This second system will follow a similar path as the first
with rapid deepening expected as it moves northwards, parallel to
the California coastline. This will bring another round of strong,
impactful winds with it but wind gusts will be slightly weaker than
they were compared to the first system. Multiple rounds of moderate
to heavy rain will move through the Bay Area and the Central Coast
with this system. The WPC has issued a slight risk of excessive
rainfall for much of our area Wednesday and a marginal risk of
excessive rainfall for the Big Sur coastline on Thursday. Given the
more widespread moderate to heavy rain for this system, flooding
will be more likely across urban areas with rises in smaller
streams/creeks and mainstream rivers likely (especially the Russian
River and Napa River). With the return of moderate to heavy rain and
strong winds, additional power outages and downing of trees is
expected Wednesday night into Thursday.

The biggest threat late Wednesday through Friday will be the
potential for severe weather, including the risk of weak tornadoes
and waterspouts. The SPC has issued a marginal risk of severe
thunderstorms and a 2% chance of tornadoes/waterspouts along our
entire coastline. The highest risk for a weak tornado/waterspouts
will be from embedded thunderstorms within the main rain band as the
cold front passes through our CWA. That being said, guidance shows
the potential for isolated cells to develop in the wake of cold
frontal passage which also display potential for severe thunderstorm
development and rotation. This system looks even more favorable than
the first system with much more instability (higher MUCAPE values
over a much larger area) and continued strong low level shear
between 30 to 45 knots. A marginal risk of severe thunderstorms
continues for the Big Sur coastline into Friday while the rest of
our region has general thunderstorms. The highest potential for
thunderstorms would be along the coastline in the late morning to
afternoon timeframe with the potential for a weak tornado or
waterspout continuing. Make sure you have multiple ways to receive
any warnings that may be issued during both the Tuesday-Wednesday
and late Wednesday-Friday systems in the event that severe
thunderstorms are able to develop. This is the most favorable
environment for severe weather that we have seen in quite a while.

Rain showers continue into Friday before diminishing heading into
the weekend. This does not mean the storm door is closing with long
range guidance showing the potential for additional systems late
December into early January.

&&

.AVIATION...
(06Z TAFS)
Issued at 1001 PM PST Tue Dec 23 2025

Conditions will rapidly deteriorate overnight as a strong frontal
system moves quickly through the region. Despite breezy S winds
continuing, conditions will improve Wednesday morning into the
early afternoon before deteriorating again by the sunset hours.
Overall a complicated forecast for timing given the several rounds
of weather that are expected over the next 24-36 hours. Starting
tonight, there will be multiple rounds of very gusty S winds to
35+ kts and heavy rain. Tried to nail down timing in TAFs, but may
shift by an hour each way. This is a high confidence event in
terms of occurrence, but moderate confidence in timing. Chance for
thunderstorms exists at all terminals through this TAF period.
However, confidence only high enough to include later in the
period. TS hazards include downbursts and isolated occurrences of
waterspouts.

Vicinity of SFO...Winds expected to increase sharply tonight as
the surface low and associated cold front approach the Bay Area.
Anticipating an intense band of very gusty S winds and heavy rain
in the pre-dawn hours. Decent confidence that there will be a lull
in activity through the morning rush, though winds will still be
southerly for the duration of the TAF period. Next round of gusty
S winds and pockets of heavy rain anticipated by the sunset hours
Wednesday. Thunderstorm potential appears higher with this round
late Wednesday.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Several rounds of quick-moving heavy
rain and gusty S/SE winds will occur throughout the TAF period.
Expect conditions to improve Wednesday morning before
deteriorating again by the sunset hours. Thunderstorms appear more
likely during this later period with the potential for waterspouts
over the Monterey Bay and near shore.

&&

.MARINE...
(Tonight through next Monday)
Issued at 908 PM PST Tue Dec 23 2025

...EXTREMELY HAZARDOUS MARINE CONDITIONS EXPECTED TONIGHT AND
EARLY WEDNESDAY MORNING...

Conditions are rapidly deteriorating over the waters as a
significant surface low pressure system enters the waters. Gale-
force winds with frequent gusts near 60 kts are expected across
the coastal waters. This system will move through quickly
overnight with lingering impacts Wednesday morning. These winds
will build very rough, steep waves with a significant wave height
near 20 feet. Another gale-force low is anticipated to enter the
waters early Thursday morning. If your vessel is not able to
handle these conditions return to port or seek protected waters as
soon as possible.

&&

.BEACHES...
Issued at 429 AM PST Tue Dec 23 2025

The strong winds along the coast will result in hazardous beach
conditions. A Beach Hazards Statement has been issued for the
coast from 4PM Tuesday through 4AM Wednesday. 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.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through late Thursday night for CAZ006-
     505-509-529-530.

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

     High Wind Warning until 4 AM PST Wednesday for CAZ006-502-503-
     505-509-516-517-528>530.

     Wind Advisory until 4 AM PST Wednesday for CAZ504-506-508-510-
     512>515-518.

PZ...Gale Warning until 3 AM PST Wednesday for SF Bay N of Bay Bridge.

     Gale Warning from 3 PM Wednesday to 3 AM PST Thursday for SF Bay
     N of Bay Bridge.

     Storm Warning until 3 AM PST Wednesday for Mry Bay-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 Reyes to Pigeon Pt 0-10 nm.

     Storm Warning until 3 AM PST Thursday for Pigeon Pt to Pt Pinos
     0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...Flynn
LONG TERM....Kennedy
AVIATION...Behringer
MARINE...Behringer

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