Altadena, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

018
FXUS66 KMTR 250658
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1058 PM PST Wed Dec 24 2025

...New SHORT TERM, LONG TERM, MARINE...

.KEY MESSAGES...
Updated at 1052 PM PST Wed Dec 24 2025

 - Strong and damaging winds continue overnight through Thursday
   evening.

 - 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 evening. 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 1052 PM PST Wed Dec 24 2025
(Tonight through Friday)

Don`t let your guard down, the line of showers and thunderstorms
with strong winds that swept through our area earlier this
(Wednesday) evening was only a precursor to what is expected to
be the most impactful line of storms yet, that is currently about
to enter our outer marine zones about 100mi offshore. Impacts for
the next line are expected to be felt by Midnight PST, with
another round of strong wind, periods of heavy rain with the
potential of low top supercells producing waterspouts that could
move onshore as short-lived tornadoes or straight line winds up
to 80 MPH or higher. The High Wind Warning remains in place until
10 AM PST Thursday (Christmas) morning and may be extended. Our
Flood Watch remains in place until Friday night at 10 PM PST. The
SPC continues to have our entire Pacific Coast line in a Marginal
Risk for Severe Thunderstorms through early Friday morning at 4
AM. That means, the line off showers and thunderstorms progged to
move onshore as early as late afternoon Thursday into the evening
hours may be just as impactful as the one currently on our door
step. That means all hazards mentioned above are in play through
at least tomorrow night, along with the dangerous beach hazards
and gale to near storm force winds over both our coastal and outer
waters. If traveling Christmas day or night, expect extensive
travel delays, along with power outages and urban/nuisance
flooding.

&&

.LONG TERM...
Issued at 1052 PM PST Wed Dec 24 2025
(Friday night through next Wednesday)

*Long term discussion remains unchanged from Wednesday afternoon
 update*

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...
(06Z TAFS)
Issued at 916 PM PST Wed Dec 24 2025

Radar and satellite imagery show showers across the forecast area
including recent isolated thunderstorms. A strengthening low will
approach far northern California and the Pacific Northwest tonight
through Christmas Day/Night. Southerly winds will re-intensify to
similar speeds last night. Expect low level wind shear through the
evening and overnight, winds easing later Christmas Day. The frontal
system will result in showers, occasionally heavy, including a
chance of thunderstorms across the area tonight through Christmas
Day/Night.

Vicinity of SFO...VFR-MVFR with showers and a chance of a
thunderstorm tonight and Christmas Day. Southeasterly wind
continuing ahead of the next strong frontal system arriving later
tonight and early Christmas Day. Southeasterly wind increasing
upwards to around 35 knots continuing to 20z Christmas Day, easing
later in the day.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR-MVFR with showers and a chance of a
thunderstorms tonight and Christmas Day. Southeasterly winds 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 Tuesday)
Issued at 1052 PM PST Wed Dec 24 2025

...HAZARDOUS MARINE CONDITIONS CONTINUE INTO EARLY FRIDAY...
Southeast breezes across the coastal waters will re-intensify to
sustained gales from the south by midnight. These dangerous winds
will be accompanied by a 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 until 10 AM PST Thursday for CAZ006-503-505-
     509-517-528>530.

     Wind Advisory until 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...JM
LONG TERM....JM
AVIATION...Canepa
MARINE...Canepa

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, X, and YouTube at:
www.facebook.com/nwsbayarea
x.com/nwsbayarea
www.youtube.com/nwsbayarea