553
FXUS66 KMTR 230004
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
404 PM PST Sat Feb 22 2025

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 1111 AM PST Sat Feb 22 2025

Chance of very light rain in the North Bay tonight into Sunday and
again on Monday. Otherwise, dry and warm through the middle of next
week. Chance of rain returns later next week with a cutoff low
approaching the state, although details are still highly
uncertain.

&&

.SHORT TERM...
(This afternoon through Sunday)
Issued at 1111 AM PST Sat Feb 22 2025

Satellite imagery reveals coastal stratus lingering in the North Bay
and San Mateo Peninsula coastlines, while scattered cirrus persists
over much of the region. If there is anything vaguely exciting about
the short-term forecast for our region, it`s found up in the
northern fringes of Sonoma and Napa Counties. A plume of moisture is
impacting the Pacific Northwest, with the Eureka radar also showing
rain just offshore of the North Coast. The edges of the moisture
plume could bring light rain to the northern regions of Sonoma and
Napa counties beginning tonight into Sunday. Emphasis on light rain,
with the rainfall totals only around a few hundredths of an inch at
most.

Elsewhere in the region, the big story is dry and warm weather
through the weekend. Highs today range from the low to mid 70s today
in the inland valleys to the middle to upper 60s closer to the coast.
The low temperatures are also inching upwards for Sunday morning,
ranging from the middle 40s to the lower 50s in the lower
elevations, while Sunday`s highs reach the upper 70s across the
southern Salinas Valley, generally remaining similar to today`s
elsewhere.

&&

.LONG TERM...
(Sunday night through next Friday)
Issued at 1111 AM PST Sat Feb 22 2025

Another round of light rain comes into the North Bay on Monday, with
an upper level low off the Pacific Northwest becoming more defined
in the model output since yesterday. The main impacts to the
forecast are a slight increase in rain totals in the North Bay, to
around a tenth of an inch in favored locations in the Sonoma coastal
ranges, and a dip in temperatures across the region. Monday`s highs
reach the lower 60s in the North bay valleys, the upper 60s the
middle 70s in the inland valleys elsewhere, and the lower to middle
60s along the coast. As the disturbance passes, upper level ridging
returns to the region and resumes our warming trend, with high
temperatures in the inland valleys reaching the middle to upper 70s
by Wednesday.

By the middle of the week, a trough moving through the northern
Pacific deepens and cuts off as it approaches the state. At this
point, significant differences between models, and among the
ensemble solutions from the models, make the forecast highly
uncertain. Looking at the ensemble means, the American GEFS model
places a weaker low through the Central Coast by Thursday, the
Canadian GEPS model places an even weaker low around the same place
and timeframe, while the European ECMWF model further deepens the
low, places it closer to southern California, and delays its impact
to Friday. The ensemble model cluster analysis further supports
these claims with the European ensemble members tending to support a
fully cut off low off the coast of California on Thursday, while the
American ensemble members supporting a broader trough or weaker
cutoff low that gets closer to the coast, and the Canadian ensemble
members tending to support solutions that more resemble a shortwave
trough. At this point, there is a chance for rain late Wednesday
through early Friday, but anything more specific than that would be
beyond the current state of the forecast certainty. Expect further
refinements to the forecast through the next few days.

&&

.AVIATION...
(00Z TAFS)
Issued at 404 PM PST Sat Feb 22 2025

Satellite shows high level clouds have reached the Bay Area and are
starting to reach the Central Coast. Persistent low lying clouds
continue in the vicinity of KHAF with LIFR visibilities and ceilings
expected to continue through the majority of the TAF period.
Scattered light showers are possible in the vicinity of KSTS (low to
moderate confidence) and KAPC (low confidence). Guidance indicates
that patchy IFR to LIFR CIGs may develop overnight and push into the
SF Bay, Monterey Bay, and inland valleys with low to moderate
confidence that this will impact OAK, SFO, SJC, MRY, and SNS. Higher
confidence in IFR to LIFR conditions at STS and HAF overnight where
high RH values and light winds are contributing to elevated fog
development potential. Winds generally stay light and variable
through the TAF period with moderate northwest winds expected to
develop by tomorrow afternoon.

Vicinity of SFO...VFR with low to moderate confidence in patchy IFR
conditions developing overnight. Moderate NW winds continue through
the day today and again tomorrow with lighter, at times variable,
winds expected overnight. Ensemble guidance is mixed on if SFO will
be impacted by IFR CIGs. The majority of models show IFR CIGs
staying along the coastline and across the San Pablo Bay (north of
SFO and OAK). However, the NBM shows patchy IFR CIGs filtering into
the south San Francisco Bay which would result in a scenario more
likely to bring IFR conditions to SFO. The most likely timeframe to
watch for IFR conditions at SFO will be 12Z to 18Z.

SFO Bridge Approach...Some potential for IFR CIGs to filter into the
south San Francisco Bay between 12Z and 18Z. CIGs over the bay may
clear out slightly faster than at the terminal itself (NBM looking
to clear the bay out closer to 20Z compared to 18Z). Otherwise,
forecast is similar to SFO.

Monterey Bay Terminals...VFR with some potential for lowered CIGs to
develop overnight. Patchy MVFR to IFR-LIFR CIGs are expected
overnight. Ensemble guidance places the highest confidence in
lowered CIGs remaining directly along the coastline but patchy
lowered CIGs may move inland for short periods of time. Guidance
indicates slightly higher confidence in lower clouds extending into
the Salinas Valley but some uncertainty remains as to if it will
reach SNS. Low to mid level clouds will start to push in now (00Z)
through 06Z with 06Z to 18Z the most likely timeframe for lowered
CIGs to develop in the vicinity of MRY and SFO. Moderate NW winds
will weaken overnight, becoming light and at times variable, before
moderate NW flow returns again tomorrow during the day.&&

.MARINE...
(Tonight through next Friday)
Issued at 404 PM PST Sat Feb 22 2025

There is a chance for light rain tonight into Sunday and again on
Monday across the northern waters. Otherwise, winds and sea
heights will remain relatively calm into early next week. A new,
moderate northwesterly swell enters the waters by Tuesday,
causing seas to build up to 10 to 12 feet.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Kennedy
MARINE...RGass

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