Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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473
FXUS66 KMTR 281730 AAA
AFDMTR

Area Forecast Discussion...UPDATED
National Weather Service San Francisco CA
930 AM PST Fri Feb 28 2025

...New UPDATE...

.SYNOPSIS...
Issued at 259 AM PST Fri Feb 28 2025

Warm again today. Cool and wet weather returns for the weekend and
lasts through much of the next work week.

&&

.UPDATE...
Issued at 929 AM PST Fri Feb 28 2025

Overall, the short term forecast remains in good shape, with just
a couple of aesthetic changes. An upper low continues to churn
off the Southern California Bight. This feature continues to send
largely mid and upper level cloud cover northward, especially
across the Interior Central Coast. 12 UTC soundings from Oakland
and Vandenberg shows a dearth of dry air (a little less dry
farther south) which should translate to a mostly rain-free day
today (Friday). The satellite presentation does indicate a more
cumuliform type look to the clouds, suggesting the presence of
mid/upper level instability. With some spotty reports of virga,
I`ve elected to throw in a mention of sprinkles across southern
Monterey and San Benito counties. This shouldn`t translate to much
fan fare, but I wouldn`t be surprised if a few drops of rain are
observed later this morning and into the afternoon.

Outside of adjusting sky cover and Wx grids, the rest of the
forecast remains unchanged. Updated products have been shipped.


&&

.SHORT TERM...
(Today and tonight)
Issued at 259 AM PST Fri Feb 28 2025

It has been a quiet night.

We`ve been seeing mostly high-level clouds rotating around a cut-off
low to the southwest, but otherwise quiet.

The increasing cloud cover and the pattern change offering more
onshore flow will prevent temperatures from seeing the 80s like
yesterday. Highs will still be above average with widespread 60s and
into the 70s for the more interior areas. Things will steadily cool
into the night with the potential for fog building in the early
night. The stronger chances for fog look to fall in the North Bay
valleys, with the best chances being around Santa Rosa.

&&

.LONG TERM...
(Saturday through Thursday)
Issued at 259 AM PST Fri Feb 28 2025

Fog dissipates in late Saturday morning with the next cold front
approaching that evening, bringing widespread light rain. The parent
low pressure system of this front builds in quickly in the post
frontal environment, keeping the rain chances pretty persistent
through the weekend and into Monday. Potential for shattered
thunderstorms increases as the low moves through the area, with the
best chances hitting around 15% near the Monterey Bay and along the
Big Sur Coast Monday morning. Rainfall totals from the Saturday
through Monday rain event look to range between 0.10" to 0.50" with
higher elevations in the Santa Cruz Mtns and in the Santa Lucias
getting closer to 0.75"

After a brief pause, another rain-maker arrives mid Tuesday. Overall
model and ensemble confidence is good that light to moderate rain
will push through along another cold front and low pressure combo.
There also looks to be a fair consensus for rain chances lasting
through Friday. The main point of forecasting concerns for this one
is the orientation of the low as it builds in, which could make the
focus of the highest rainfall amounts to shift in the next few
forecast updates. As of the current forecast, the low pressure moves
inland at the Big Sur Coast, offering the higher rain amounts in the
Santa Lucias (1.50"-2"). However, if the low turns inland sooner,
the North Bay Coast would be the rainfall leader. This is all to say
that there is still a fair amount of polishing needed to be done in
the longer term portion of the forecast.

&&

.AVIATION...
(12Z TAFS)
Issued at 419 AM PST Fri Feb 28 2025

This upcoming TAF cycle will be a tale of two pressure systems:
broad area of high pressure across the West and a cutoff low off
the coast of Southern California. The cutoff low is responsible
for the high clouds overhead and the offshore flow. As it
progresses eastward, it`ll take the clouds with it and diurnal
winds will return. As onshore flow returns, so too does the
humidity. With higher relative humidity and a lack of overhead
clouds under a broad area of high pressure (subsiding air), the
marine layer will likely be compressed/shallow with low ceilings
and visibilities with conditions expected to be the worst near
the coast.

Vicinity of SFO...Currently VFR and calm. The sea breeze will return
this afternoon, prevailing through the TAF period. Moderate
confidence in a reduction to MVFR by late tonight.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Currently VFR with easterly flow at MRY and
VFR with drainage flow at SNS. Onshore flow will develop by mid-
morning, prevailing through the TAF period. High confidence in a
reduction in flight category to IFR by late tonight.

&&

.MARINE...
(Today through Wednesday)
Issued at 259 AM PST Fri Feb 28 2025

A moderate northwesterly breeze on Friday will increase to a fresh
northwesterly breeze on Saturday. Significant wave heights will
fluctuate between moderate and rough through Tuesday. Widespread
rainfall can be expected Saturday through Monday with a slight
chance for thunderstorms Sunday and Monday.

&&

.BEACHES...
Issued at 419 AM PST Fri Feb 28 2025

Hazardous beach conditions are expected Friday through Monday due to
building long period westerly swell supporting breaking waves of 14-
19 feet. This will be both a beachgoer and a mariner threat.
Everyone should remain out of the water due to life-threatening
surf conditions. Stay off of jetties, piers, and other waterside
infrastructure, keep pets on a leash and away from the water, and
never turn your back on the ocean!

Sarment

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement from 9 PM PST this evening through
     Saturday morning for CAZ006-505-509-530.

     High Surf Advisory from 9 AM Saturday to 9 PM PST Monday for
     CAZ006-505-509-530.

     Beach Hazards Statement from 9 PM PST this evening through
     Monday evening for CAZ529.

PZ...Small Craft Advisory from 9 AM to 3 PM PST Saturday for Pigeon
     Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM.

     Small Craft Advisory until 3 PM PST this afternoon for Pigeon Pt
     to Pt Pinos 10-60 NM.

&&

$$

UPDATE...Bain
SHORT TERM...Murdock
LONG TERM....Murdock
AVIATION...Sarment
MARINE...Sarment

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