Technical NOAA Weather Discussion

FXUS66 KMTR 271807
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1007 AM PST Tue Jan 27 2026

...New AVIATION...

.KEY MESSAGES...
Updated at 319 AM PST Tue Jan 27 2026

 - Mild with increasing cloud cover through the day

 - Increasing rain chances tonight through Wednesday morning for
   the North Bay into Bay Area, with light amounts between
   0.1"-0.2" expected where it does rain

 - Drier conditions and weak offshore flow return quickly by
   Wednesday afternoon

 - Beach Hazards Statement for increased risk of sneaker waves 
   and riptides Wednesday night through Friday Morning

&&

.UPDATE...
Issued at 850 AM PST Tue Jan 27 2026

It was a chilly morning across the interior valleys where 
temperatures dropped into the mid to upper 30s. Portions of far 
interior Monterey County (vicinity of Fort Hunter Liggett) dropped 
below freezing overnight. Temperatures are warming up with fog 
currently being reported at the Livermore Airport. Light rain 
remains on track to return to the North Bay this evening into the 
overnight hours. Precipitation totals remain light with between 0.25-
0.50" in the North Bay and up to 0.10" across San Francisco and 
portions of the East Bay/San Mateo County. No impacts are expected 
from this due to the substantial dry spell in between our last 
system and this current one.

&&

.SHORT TERM...
Issued at 319 AM PST Tue Jan 27 2026
(Today and tonight)

The 00z KOAK sounding recorded 0.43" PWAT last night with HiRes 
short-term soundings indicating similar or lower values until after 
sunrise this morning in the North Bay, with the boundary layer not 
beginning to saturate until later this morning into the afternoon 
that far north. Prefrontal drizzle or light rain is possible along 
the North Bay coastal ranges later this morning into the afternoon 
with the added lift. Otherwise, the bulk of the rainfall is expected 
to move inland after sunset tonight, and shift east by sunrise 
Wednesday morning. Slight chance PoPs extend as far south as the 
Santa Cruz mountains later today and tonight, however rain totals 
south of the North Bay are expected to be less than 0.1" where it 
does rain. Inland areas of the North Bay like Santa Rosa are likely 
to see around 0.20" (mean hi-res ensemble %) with higher end 
reasonable amounts near 0.30" (hi-res 75th%), thus little impacts
beyond wetting rainfall are expected. Lesser amounts are expected
farther east as the progressive shortwave trough moves out of our
area to the east.

&&

.LONG TERM...
Issued at 319 AM PST Tue Jan 27 2026
(Wednesday through Monday)

The progressive upper level trough moving across the North Bay will 
shift east Wednesday morning with a ridging pattern developing 
quickly in its wake. Weak offshore flow will return as a result with 
another dry airmass filling in for the remainder of the work week 
into the beginning of weekend. Long period westerly swell and 
increasing wave heights will result in an increased risk of sneaker 
waves and riptides along with breaking waves up to 19ft Wednesday 
night through Friday morning, with a Beach Hazards statement issued 
for that time period, see the Beach Hazards discussion for more 
details. Slight chance PoPs return as soon as late Saturday night 
into Sunday for the North Bay once again, however a lack in 
consensus of the location, depth and timing of the developing trough 
leaves far more questions than answers at this point.

&&

.AVIATION...
(18Z TAFS)
Issued at 1006 AM PST Tue Jan 27 2026

Mostly VFR conditions across the region at this hour. As a weak 
frontal boundary approaches the region look for conditions to 
deteriorate around mid afternoon across the North Bay and then 
late this evening and overnight across the Bay Area terminals. At 
this time, mostly MVFR conditions are expected over this region 
with fog returning early Wednesday morning at STS and LVK. Looking
less likely MRY and SNS will receive anything more than VCSH and 
brief MVFR conditions this evening and into early Wednesday 
morning. VFR conditions are expected by Wednesday afternoon in 
wake of the frontal passage. 

Vicinity of SFO...VFR conditions will prevail through around 03Z 
Wednesday when conditions become more likely to reduce to MVFR as 
rain showers move across the region. A greater probability will be
in the 06-09Z Wednesday timeframe for MVFR (temporary IFR if and 
when RA is present) as the main rain band is forecast to move 
across the terminals. MVFR will persist through about 18Z 
Wednesday before improving to VFR as skies clear in wake of the 
passing frontal boundary.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Mostly VFR through the TAF period. 
Drainage winds (southeasterly) once again at SNS will become 
onshore by this afternoon. A weakening frontal boundary will 
approach late this evening increasing the probability for MVFR 
conditions. However, confidence is only moderate at this time. 
There is greater probability for VFR conditions by 18Z Wednesday. 

&&

.MARINE...
(Today through Sunday)
Issued at 850 AM PST Tue Jan 27 2026

Light to moderate southerly flow will prevail over most of the
waters as a weak cold front approaches from the west today through
early Wednesday morning. This will bring light rain to the
northern coastal waters through Wednesday morning. Winds will be
moderate to breezy north of Point Reyes with locally hazardous
conditions for small craft. Winds diminish on Wednesday and switch
to northerly that night. Moderate seas will prevail through
Tuesday, but build rough to very rough Wednesday night.

&&

.BEACHES...
Issued at 359 AM PST Tue Jan 27 2026

Long period swells with low wave  heights begin to arrive on 
Wednesday, but wave heights begin to increase that night while 
periods stay long leading to hazardous conditions. A Beach 
Hazards Statement has been issued from 09 PM Wednesday through 09 
AM Friday. Significant wave heights look to range from 14 to 19 
feet. The main threat will be from sneaker waves and rip currents.
Stay off of jetties, piers, rocks, and other waterside 
infrastructure. Remain out of the water to avoid hazardous surf 
and NEVER turn your back on the ocean.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement from Wednesday evening through Friday 
     morning for CAZ006-505-509-529-530.

PZ...Small Craft Advisory until 9 PM PST this evening for Pt Arena to 
     Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.

     Small Craft Advisory from 9 AM Thursday to 3 AM PST Friday for 
     Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm.

     Small Craft Advisory from 3 AM Thursday to 3 AM PST Friday for 
     Pt Arena to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...JM
LONG TERM....JM
AVIATION...RGass
MARINE...RGass

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Prepared by Boulder-Creek.com Weather at: Tue Jan 27 12:30:03 PST 2026
From the National Weather Service