FXUS66 KMTR 242352
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
352 PM PST Wed Dec 24 2025
...New AVIATION, MARINE, BEACHES...
.KEY MESSAGES...
Updated at 1238 PM PST Wed Dec 24 2025
- Strong and damaging winds return overnight and continue through
Thursday.
- A flood watch remains in effect through Friday evening across
the region. The main threat is flash flooding and landslides
from high rain rates.
- Slight chances for severe thunderstorms begin this evening and
continue through Thursday. 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 this weekend after the storms
break.
&&
.SHORT TERM...
Issued at 1238 PM PST Wed Dec 24 2025
(This evening through Thursday)
The skies have cleared better than expected today giving us a
short, but remarkably nice break between last night's wind storm
and the upcoming system. The initial round of showers could reach
the Santa Cruz/San Mateo coast as early as 3 PM. This is a
prefrontal trough that won't bring the primary impacts expected
overnight, but is currently producing thunderstorms over the
coastal waters that could survive until landfall. With the bonus
sunshine, temperatures are climbing higher than expected and
that's translating to a better convective environment. Santa Rosa
has been under clear skies since the sun rose this morning and is
currently reporting a temperature of 61 degrees, well above the
56 we had for the maximum today. This extra surface heating will
play a role in the instability going into the evening hours. The
environment ahead of tonight's storms look pretty good for
thunderstorms and even tornadoes. The 18Z RAP shows the following
parameters at SFO compared to the preferred value for supercell
tornadoes in parentheses. 0-1km shear: 40 kts (20), MLCAPE: 209
J/kg (1500), Significant Tornado Parameter: 0.3 (1.0), MLCIN: -2
(>-25), Effective Storm Relative Helicity: 242 m2/s2 (150),
Effective Bulk Wind Difference: 44 kts (40). This is a high-shear,
low CAPE set-up, but the increased surface temperature and high
dew points from last night's rain are helping the surface based
convection chances. In fact, our next shift just walked in and one
of the meteorologists said it feels like Kansas in May out there.
The main impacts are expected through the overnight hours and will
be similar to last night. The winds may be a notch lower, but the
severe thunderstorms chances are a notch higher. The other
difference compared to last night is how much longer the winds
will linger into the following day. The parent low pressure system
will not push inland, but rather linger off the coast while
gradually weakening. This will keep southerly winds elevated
through the day Thursday, while pushing through a couple bands of
showers. The peak of the impacts are still expected in the middle
of the night, but we won't get the quick reprieve that we saw
this morning. It will still be breezy while the kids try out their
new bikes and basketballs Christmas morning. Scattered showers
will be a threat through the day.
&&
.LONG TERM...
Issued at 1238 PM PST Wed Dec 24 2025
(Thursday night through next Tuesday)
Starting in the early morning Friday, winds and shower activity
will gradually decrease as the low pressure system offshore opens
up into a trough and moves into northern Oregon. The associated
surface trough axis will move across the Bay Area Friday evening.
This will finally flip the winds back to northerly, bringing
drier, cooler weather for the weekend. The 1000-500 mb thickness
actually increases this weekend, with the cooling coming mainly from
enhanced radiation during in the cloudless nights. Sunday through
Tuesday look particularly calm, clear and cool as a 500 mb ridge
sets in. The next troughing pattern looks probable on the 1st or
2nd, just in time for King Tides. There's no strong signal for
major impacts yet, but the CW3E ECCC AR Activity tool shows higher
than normal chances for atmospheric rivers through the first half
of January.
&&
.AVIATION...
(00Z TAFS)
Issued at 352 PM PST Wed Dec 24 2025
VFR prevails, however radar and satellite imagery show widely
scattered showers across the forecast area including recent
isolated thunderstorms approaching the coastal waters from the
southwest. A strengthening low pressure system will approach far
northern California and the Pacific Northwest tonight through
Christmas Day/Night. As mentioned in the previous discussion,
southerly winds will re-intensify to similar speeds last night.
Expect low level wind shear developing through the evening and
overnight, winds easing later Christmas Day. The frontal system
will result in rain showers, occasionally heavy, including a
chance of thunderstorms across the area tonight through Christmas
Day/Night.
Vicinity of SFO..VFR then MVFR-IFR developing mid evening with
showers and a chance of a thunderstorm. Showers and a chance of a
thunderstorm continue tonight and Christmas Day. Southeasterly
wind generally continuing ahead of the next strong frontal system
arriving later tonight and early Christmas Day. Southeasterly wind
increasing upwards to around 35 knots by 05z-09z and continuing
to 20z Christmas Day, easing later in the day.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR then MVFR developing mid to late
evening with showers and a chance of a thunderstorms. Showers and
a chance of a thunderstorms continue tonight and Christmas Day.
Southeasterly winds continuing ahead of the next strong frontal
system arriving later tonight and early Christmas Day; gusts
upwards 30-35 knots, easing later in the day.
&&
.MARINE...
(Tonight through next Monday)
Issued at 324 PM PST Wed Dec 24 2025
...HAZARDOUS MARINE CONDITIONS CONTINUE INTO EARLY FRIDAY...
Moderate southeast breezes across the coastal waters will
gradually re-intensify to sustained gales from the south by
midnight. These dangerous winds will be accompanied by a good
chance for thunderstorms and possible waterspouts through the
early morning hours Thursday. Seas will rebuild to very rough from
the choppy wind waves. These hazardous seas will linger through
Friday, reinforced by a moderate westerly swell. If your vessel is
not able to handle these conditions return to port or seek
protected waters as soon as possible.
&&
.BEACHES...
Issued at 325 PM PST Wed Dec 24 2025
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...Flood Watch through Friday evening for CAZ006-502>506-508>510-
512>518-528>530.
Beach Hazards Statement through late Thursday night for CAZ006-
505-509-529-530.
High Wind Warning from 8 PM this evening to 10 AM PST Thursday
for CAZ006-503-505-509-517-528>530.
Wind Advisory from 8 PM this evening to 10 AM PST Thursday for
CAZ502-504-506-508-510-512>516-518.
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...Flynn
LONG TERM....Flynn
AVIATION...Canepa
MARINE...Canepa/Flynn
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Prepared by Boulder-Creek.com Weather at: Wed Dec 24 18:30:03 PST 2025
From the National Weather Service
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