FXUS66 KMTR 241218
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
418 AM PST Wed Dec 24 2025
...New UPDATE...
.KEY MESSAGES...
Updated at 208 AM PST Wed Dec 24 2025
- Hazardous and damaging winds continue through the morning, with
a lull during the day before strong winds resume tonight
through Thursday.
- Flood Watch remains in effect through Friday evening across the
region. The main threat is flash flooding from high rain rates.
- Slight chances for severe thunderstorms continue through
Thursday with thunderstorm risks continuing through Friday.
Severe threats include damaging wind gusts and possible
tornadoes.
- Dangerous beach and marine conditions continue through Friday
across the Pacific coast and adjacent beaches.
- Cold temperatures settle in behind the storm systems for the
weekend into the beginning of next week.
&&
.UPDATE...
Issued at 416 AM PST Wed Dec 24 2025
Main frontal band continues to move through the East Bay, South
Bay, and Monterey Bay regions. Several reports of roadway flooding
have been received from across the region. All wind products have
been extended through 8 AM today, with high confidence of new
wind products issued for tonight and Thursday afterward. Otherwise
forecast remains the same. Operations team continues to be in
warning operations.
DialH
&&
.SHORT TERM...
Issued at 208 AM PST Wed Dec 24 2025
(Today and tonight)
The strong winds, offshore thunderstorms, and scattered reports of
flooding through the night so far can all be traced to a cyclonic
system off the North Coast, moving parallel to the West Coast as it
crosses into the waters off Oregon. The associated frontal band is
moving across the coastal waters, with thunderstorms along the
narrow cold-frontal rain band prompting the issuance of Special
Marine Warnings. On land, the strongest gusts reported so far
tonight were 95 mph at the Pine Mountain Fire Road PG&E station in
the highlands of marin County, 93 mph at the Lone Tree Towers PG&E
station in the very northeastern corner of San Benito County, and 89
mph at the Oak Ridge RAWS in northwestern Sonoma County. The strong
winds will continue through the next few hours with the winds
decreasing rapidly once the front moves through the region. A High
Wind Warning is out for the coastal regions, and a Wind Advisory for
the interior, until 4 AM this morning.
There is also a slight, but non-zero, chance for severe
thunderstorms across much of the region today, with the SPC outlook
showing a Marginal risk for severe thunderstorms across the coastal
region and inland into the Salinas Valley, the area towards the west
of the Diablo Range, and the Sonoma County valleys. The severe
weather chances remain elevated through the pre-dawn hours this
morning as strong ascent and a robust coastal jet will enable severe
winds to mix to the surface within the strongest convection,
resulting in damaging wind gusts. In addition, the special 6Z
sounding from Oakland does show a little bit of directional shear
near the surface, meaning that any cell able to tap into this
helicity could spin up a brief tornado.
Finally, the system continues to bring chances for heavy rainfall,
generally within the convective cells that develop through the
morning hours. The Flood Watch remains in effect through Friday, but
the outlook has transitioned from a multi-day period of steady,
intense rain resulting in river flooding concerns, to an elevated
risk of flash flooding across the region.
As the front moves through the region, the rain should diminish,
winds should die down, and the chances for convection decrease for
the rest of the day. This might be a good time to take stock and
make any quick repairs or other necessary actions. Emphasis on the
word "quick" though. Behind this system, another low pressure system
will develop in the eastern Pacific and approach the West Coast.
This will bring us a second round of strong winds, heavy rainfall,
and convective chances for tonight through Thursday morning. It's
likely that a new set of High Wind products will be issued for this
coming storm period once the products currently in effect expire.
In a mostly academic concern, high temperatures today will range
from the middle 50s to the lower 60s across the lower elevations,
into the upper 40s to the lower 50s in the higher elevations.
&&
.LONG TERM...
Issued at 208 AM PST Wed Dec 24 2025
(Thursday through Tuesday)
Strong winds and periods of heavy rain will persist into Thursday
(Christmas Day) and Friday as the low pressure system meanders off
the North Coast, and the Marginal risk for severe thunderstorms
continues for the Central Coast through the day, with severe wind
gusts and brief tornadoes being the main threats. The extended
period of more moderate and heavy rain across the region will result
in increased flooding concerns, especially within urban areas with
rises in small creeks and streams and mainstem rivers likely,
particularly within the North Bay where more antecedent rainfall has
fallen. The return of the strong winds coupled with the more
saturated soils will also increase the risk for additional power
outages and downed trees into Friday. Make sure you have multiple
ways to receive warnings through Friday in case severe thunderstorms
develop. This is especially important as the increased risk for
power outages could mean that some communication systems could be
impacted, especially in rural and remote regions.
Later on Friday, the low pressure system will degrade into a trough
as it approaches the California coast, with lingering showers
continuing into Saturday morning. Behind the parade of systems, cold
temperatures will develop for the weekend into the early part of
next week, with low temperatures dropping into the middle to upper
30s across the inland valleys. Meanwhile, the storm door remains
open with long range guidance suggesting the potential for
additional systems through the early portion of January.
&&
.AVIATION...
(12Z TAFS)
Issued at 355 AM PST Wed Dec 24 2025
The main rain band, which offers the strongest winds and heaviest
rains is exiting the area and pushing east. Conditions improve
through the morning into the early afternoon before deteriorating
again in the evening as showers and storms arrive across the
region. 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.
Additional concerns will be with LLWS with many TAF sites seeing
winds aloft 30 kts stronger than the prevailing surface winds into
early Thursday.
Vicinity of SFO...Strong winds linger into the mid morning with
lingering shower activity. Winds stay breezy until the late
morning, but rebuild in the afternoon as spotty showers and storms
approach the area. Thunderstorm chances increase into the
evening, as well as winds and gusts. Storm chances and winds
reduce into the night, but rebuild again into early Thursday.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Main band of rain is passing through the
Monterey Bay and will exit to the east. Winds reduce in it's wake,
with VFR conditions expected. Lingering shower chances reduce into
the afternoon but winds and storm chances rebuild in the late
afternoon and early evening. Winds and storm chances see a brief
decrease into the night, but stronger winds and increase storm
chances are expected into early Thursday
&&
.MARINE...
(Today through Monday)
Issued at 355 AM PST Wed Dec 24 2025
...HAZARDOUS MARINE CONDITIONS CONTINUE INTO EARLY FRIDAY...
Gale- force winds are affecting the waters with the inner waters
still seeing storm- force winds. These winds are building very
rough, steep waves with a significant wave height near 20 feet.
Showers and storms will move through the waters into the mid to
late morning. Additional showers and storm chances arrive into the
evening. 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 355 AM PST Wed Dec 24 2025
The strong winds along the coast will result in hazardous beach
conditions. A Beach Hazards Statement has been issued for the
coast through 4AM 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.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...High Wind Warning until 8 AM PST this morning for CAZ006-502-503-
505-509-516-517-528>530.
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.
Wind Advisory until 8 AM PST this morning for CAZ504-506-508-510-
512>515-518.
PZ...Gale Warning until 3 AM PST Friday for Mry Bay-Pigeon Pt to Pt
Pinos 10-60 NM-SF Bay N of Bay Bridge.
Storm Warning until 3 AM PST Friday for Pigeon Pt to Pt Pinos 0-
10 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.
&&
$$
SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Murdock
MARINE...Murdock
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Prepared by Boulder-Creek.com Weather at: Wed Dec 24 06:30:02 PST 2025
From the National Weather Service
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