FXUS66 KMTR 010028
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
428 PM PST Wed Dec 31 2025
...New AVIATION...
.KEY MESSAGES...
Updated at 1247 PM PST Wed Dec 31 2025
- High astronomical tides combined with storm surge will bring
minor to moderate coastal flooding around high tide through
Sunday.
- A prolonged rainy period starts today.
- Strong southerly winds are likely Friday and into Saturday
morning.
&&
.SHORT TERM...
Issued at 1247 PM PST Wed Dec 31 2025
(This evening through Thursday)
Light to occasionally moderate rain continues to spread northward
and will increase in coverage and intensity through this evening.
This is a result of PWAT values between 1.00-1.30" advecting in from
the south as a mid/upper level cut off low remains just west of the
Central Coast. As the low pressure shifts into the Central Coast on
Thursday morning, there will be a slight chance of thunderstorms
late morning into the afternoon over this region. By late Thursday
afternoon and into the evening, rain will be more focused along the
coastal terrain as a warm front moves northward across the region.
Rain shadowed valleys may not see any rainfall from Thursday
afternoon through about Friday night.
&&
.LONG TERM...
Issued at 1247 PM PST Wed Dec 31 2025
(Thursday night through next Tuesday)
A more typical atmospheric river is set to move through the
region late Friday and into early Saturday morning. This is when
more widespread rain and stronger winds are forecast. Wind 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 night through
Saturday morning. Wind Advisories are likely during this time
frame, yet the forecast models have trended about 6 hours later
from yesterday. So, still refining the forecast as we move closer
to the event. From 4 PM Friday through 4 PM Sunday, rainfall
totals will range from 2.00- 4.00" in the coastal ranges,
1.50-3.00" in the North Bay, 1.00-2.00" in San Francisco and other
coastal areas, and generally less than 1.25" in the rain shadowed
valleys. There is generally less than a 20% chance of
thunderstorms as the main frontal band moves through and in wake
of the passage through Sunday afternoon. Given the recent rainfall
from last week, this will lead to nuisance flooding for poor
drainage areas, urban areas, and rises on flashy creeks/streams.
This will be especially so if a heavier rain shower and/or
thunderstorm where to move over any give area. However, widespread
river flooding is not anticipated at this time.
From the previous forecaster: "A new low pressure system and
associated cold front is possible Monday or Tuesday. The ensemble
clusters have differing opinions on the strength and timing of
this feature, but they all show a trough off the coast, which is
enough to keep rain chances around through the entire 7-day
forecast period. KMUX will stay in precip mode for the foreseeable
future."
&&
.AVIATION...
(00Z TAFS)
Issued at 343 PM PST Wed Dec 31 2025
A persistence forecast through the TAF period with MVFR cigs and
mostly steady light rain for all terminals. During breaks in
precip conditions could lift to VFR and during periods of more
intense rainfall, down into IFR. There is also a slight chance for
an isolated thunderstorm, with confidence too low to mention in
the TAF. Mostly easterly winds this evening and overnight, veer to
southerly and increase, becoming gusty after sunrise Thursday as
an offshore upper level system moves northeast over our
outer waters.
Vicinity of SFO...MVFR cigs expected to prevail through the
forecast period with some potential for IFR cigs/vis in times of
more intense rainfall. Winds veer from easterly this evening
through the overnight, to more southerly after sunrise Thursday
morning with occasional gusts up to 20-25mph.
SFO Bridge Approach...Similar as SFO.
Monterey Bay Terminals...MVFR cigs expected to prevail through the
forecast period, with easterly component winds this evening
becoming more southerly during the overnight period as the
offshoresystem moves northeast overnight. KSNS is expected
maintain southeast surface flow, gusty at times with the valley
influence.
&&
.MARINE...
(Today through Monday)
Issued at 859 AM PST Wed Dec 31 2025
Moderate to fresh winds and moderate seas continue into Thursday.
Widespread light rain and a low potential for thunderstorms across
the southern waters continues into Thursday. Winds rapidly
strengthen from strong to gale force by early Friday as a second,
stronger, system arrives. Periods of moderate to heavy rain and a
slight potential for thunderstorms are expected Friday into
Saturday. Winds diminish early Sunday but breezy conditions and
rain showers continue into next week.
&&
.BEACHES...
Issued at 859 AM PST Wed Dec 31 2025
Perigean spring tides (King Tides) will impact the region through
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 southerly winds, generating some storm
surge. The combination of these factors will bring minor to
moderate coastal flooding to the low-lying areas near shorelines
and tidal waterways during high tide through Sunday. At the San
Francisco tidal gauge, high tide is expected to be 2.0 ft above
normal at 8:41 AM Thursday, 2.2 ft above normal at 9:34 AM Friday,
2.2 ft above normal at 10:26 AM Saturday, and 1.8 ft above normal
at 11:18 AM Sunday. These predictions include up to 1 foot 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 until 2 PM PST Sunday for CAZ006-505-506-
508-509-529-530.
PZ...Small Craft Advisory until 3 PM PST Thursday for Pigeon Pt to Pt
Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Reyes to
Pigeon Pt 0-10 nm.
Small Craft Advisory from 9 PM Thursday to 3 AM PST Friday for
Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.
Gale Warning from 3 AM to 9 AM PST Friday for Pt Arena to Pt
Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.
Small Craft Advisory from 8 PM Thursday to 9 AM PST Friday for
Pigeon Pt to Pt Pinos 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.
Small Craft Advisory from 9 PM this evening to 3 PM PST Thursday
for Pigeon Pt to Pt Pinos 0-10 nm-Pt Arena to Pt Reyes 10-
60 NM.
Small Craft Advisory until 9 PM PST this evening for Pt Pinos to
Pt Piedras Blancas 0-10 nm.
Gale Warning from 9 PM this evening to 3 PM PST Thursday for Pt
Pinos to Pt Piedras Blancas 0-10 nm.
Small Craft Advisory from 3 AM to 9 AM PST Friday for Pigeon Pt
to Pt Pinos 10-60 NM.
&&
$$
SHORT TERM...RGass
LONG TERM....RGass
AVIATION...JM
MARINE...Kennedy
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Prepared by Boulder-Creek.com Weather at: Wed Dec 31 16:30:02 PST 2025
From the National Weather Service
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