FXUS66 KMTR 211109
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
309 AM PST Sat Feb 21 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 150 AM PST Sat Feb 21 2026
- Cold to very cold conditions this morning
- Unsettled weather with periods of rain and wind through the
long term forecast period
&&
.SHORT TERM...
Issued at 150 AM PST Sat Feb 21 2026
(Today and tonight)
Surface high pressure across the Intermountain West will dominate
our weather today. Clear skies and light winds are allowing for
efficient radiational cooling on top of an already cold air mass.
The 00z sounding observed an 850 millibar temperature of -1.35
degrees Celsius which is below the tenth percentile (-0.5 degrees
Celsius) for the date and time. Sensible weather wise this means it
will be another cold to very cold start to the day with temperatures
topping out below normal this afternoon. The combination of the
aforementioned high pressure and a developing storm force low
pressure system off the Pacific Northwest Coast will tighten the
pressure gradient and yield strong southerly winds. Gusts up to 40
mph are expected along the Pacific Coast and in the higher terrain.
The proximity to the aforementioned low will allow for pre-frontal
rain showers beginning this afternoon, primarily for the North Bay.
Rates will be light with no adverse impacts expected. South of the
Golden Gate Bridge can expect an increase in cloud cover and maybe
some drizzle. Sunday will be very similar with the most notable
difference being temperatures rebounding to near normal.
&&
.LONG TERM...
Issued at 150 AM PST Sat Feb 21 2026
(Sunday through Friday)
ECMWF and GEFS ensembles are in agreement of heights rising through
the first half of Monday with upper-level ridging across the
Intermountain West and upper-level troughing off the Pacific
Northwest Coast. The ridge will get tamped down on Tuesday; however,
there is great agreement that the region will remain under the
influence of the ridge and its positive height anomalies. A surface
low pressure system off the Pacific Northwest Coast will pull
moisture in from the tropics Monday into Tuesday. ECMWF and GEFS IVT
ensemble mean peaks near 500 kg/ms and weakens the system as it
sinks south. Southwesterly flow (from the tropics) will allow for
efficient rainfall due to the fetch of moist, warm air. As a result,
southwest facing terrain will have the highest accumulation with the
help of orographic lift with the lee side valleys experiencing the
rain shadow effect. Confidence is high that the North Bay will see
the highest rainfall totals. The trend continues to be our friend as
it shifts northward, subsequently lowering rainfall totals and
delaying the onset as it does so. As the forecast looks right now,
the Monday night into Tuesday system will bring widespread rainfall.
Minor flooding of low-lying, poor drainage, and urban areas will be
possible with ponding and slick roadways likely. Mainstem river
flooding is not expected with a low probability (less than 5%) of
occurrence. If rain rates do end up being high enough with this
system, shallow landslides will be possible. A warming and drying
trend kicks off Wednesday after the cold frontal passage with
temperatures climbing to 10 degrees above normal by Friday.
&&
.AVIATION...
(12Z TAFS)
Issued at 309 AM PST Sat Feb 21 2026
VFR conditions prevail through the TAF period with mid- to high
level clouds expected throughout the region. There is a low
confidence for MVFR conditions and isolated showers in the North Bay
valleys and the immediate coastal region, which is too low
confidence to include in the TAFs at this time. Better chances for
MVFR ceilings and showers come to the North Bay and the immediate
coast tonight into Sunday morning, just before and after the end of
the TAF period. Surface winds will remain light through the morning
before increasing from the south through the afternoon, with gusts
reaching 20-25 knots in favored areas. Tonight into Sunday morning,
some LLWS is possible, with the greatest impacts across the interior
regions.
Vicinity of SFO... VFR with mid- to high level clouds through the
TAF period. Southerly flow will increase through the afternoon with
gusts to 25 kt into the evening hours. There are some high
resolution models bringing scattered showers to the terminal area
Sunday morning, but the southwesterly approach should shield SFO
itself from any rain. Local topography makes showers more likely at
OAK.
SFO Bridge Approach... Similar to SFO.
Monterey Bay Terminals... VFR with some mid- to high level clouds
across the region and through the TAF period. Breezy southeast winds
increase this afternoon with speeds of 15-20 kt, diminishing at MRY
in the evening while breezy drainage flow continues at SNS.
&&
.MARINE...
(Today through Thursday)
Issued at 309 AM PST Sat Feb 21 2026
Expect fresh to moderate southerly breezes this morning with gale
force gusts developing by the afternoon, especially across the
northern waters. Rough to very rough seas persist starting tonight
into the beginning of next week. Rain chances increase across
northern waters tonight, becoming more widespread across the
northern waters by Saturday night, then spread farther south by
Sunday and Monday. Winds and seas begin to ease by the middle of
next week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Cold Weather Advisory until 9 AM PST this morning for CAZ504-506-
510-513-515-528.
Extreme Cold Warning until 9 AM PST this morning for CAZ514-
516>518.
PZ...Small Craft Advisory from 3 PM this afternoon to 3 AM PST Sunday
for SF Bay N of Bay Bridge.
Small Craft Advisory from 3 PM this afternoon to 9 PM PST this
evening for Mry Bay.
Small Craft Advisory until 3 PM PST this afternoon for Pt Arena
to Pt Reyes 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.
Gale Warning from 3 PM this afternoon to 3 AM PST Sunday 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 AM this morning to 3 PM PST this
afternoon for Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt
Pinos 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm.
Gale Warning from 3 PM this afternoon to 9 PM PST this evening
for Pigeon Pt to Pt Pinos 0-10 nm-Pt Pinos to Pt Piedras
Blancas 0-10 nm.
Gale Warning until 3 AM PST Sunday for Pt Arena to Pt Reyes 10-
60 NM.
&&
$$
SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...DialH
MARINE...DialH
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Prepared by Boulder-Creek.com Weather at: Sat Feb 21 06:30:03 PST 2026
From the National Weather Service
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