FXUS66 KMTR 271155
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
455 AM PDT Tue Oct 27 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 1202 AM PDT Tue Oct 27 2026
- Minor coastal flooding at high tide for Bayshore and Pacific
Coast locations through the week
- Cool conditions through the next seven days
- Rain chances late week into early part of next week
&&
.SHORT TERM...
Issued at 1202 AM PDT Tue Oct 27 2026
(Today and tonight)
Satellite imagery reveals some patchy stratus developing mainly over
the higher elevations of the Bay Area and Central Coast, but also
extending to a patch over Monterey Bay itself. Stratus development
overnight remains somewhat uncertain but some expansion is expected
through the morning hours with stratus dissipating through the late
morning and early afternoon hours.
The weather pattern continues to be dominated by a large scale ridge
with an axis over the Pacific Northwest, as an embedded low
reinforces the larger pattern and brings the troughing influence
farther south into northern and central California. Highs remain
relatively cool for this time of year with middle to upper 60s
expected in the interior valleys, the lower 70s in the warmest parts
of extreme southern Monterey County, lower to middle 60s close to
the Bays, and the upper 50s to lower 60s along the Pacific coast.
Gentle to moderate onshore winds will develop this afternoon with
gusts reaching 20 to 30 mph along the coast, through favored gaps
and passes, and at the ridgelines.
A combination of high astronomical tides and surge from thermal
expansion effects brings the risk of minor coastal flooding along
the Bayshore at the San Pablo, San Francisco, and Monterey Bays, and
the Pacific coast, at high tide today. At the San Francisco tidal
gauge, high tide is expected to be 2.1 ft above normal (7.9 ft MLLW)
at 12:15 PM Tuesday 10/27, including around 1.2 ft of surge residual
partially attributed to impacts from El Nino.
&&
.LONG TERM...
Issued at 1202 AM PDT Tue Oct 27 2026
(Wednesday through Monday)
Troughing will continue to impact the region through the work week.
The trough pattern will get reinforced through Wednesday as a cut-
off low forming over British Columbia migrates southwards, allowing
a low pressure system flowing in from the central Pacific to merge
into a trough axis that will extend down the West Coast and persist
into the upcoming weekend. The net result will be a continued
gradual cooling trend across the region with highs dipping into
the middle 50s to middle 60s across the lower elevations by the
latter part of the week.
For the Halloween weekend, confidence for significant rainfall has
decreased since yesterday, especially across the SF Bay Area, where
probabilities for rainfall have decreased to around 10-30% and
measurable rainfall chances have all but vanished. The greatest
chances for measurable rainfall remain around Monterey and San
Benito Counties, and there rain totals are expected to be light with
the probability of wetting rains (rain totals above 0.1") rather low
(below 15%). Remember that last night, NBM guidance at the Monterey
Airport suggested that for the 48 hour period beginning 5 AM PDT
Saturday the 31st and ending 4 AM PST Monday the 2nd (note the time
change, as this period includes the "fall back" from Daylight
Savings Time) suggested that the 90th percentile rainfall total (a
reasonable worst case scenario, with a 10% probability that the
final total exceeds this value) was 1.6 inches. Now, for the same
period, that 90th percentile value has dropped to 0.3 inches. It
looks like the model trend is leaning more and more towards the bulk
of the rainfall impacting southern California, and even there the
forecast remains low confidence. An active weather pattern remains
possible through the early part of next week, but any details are
hard to pin down and ensemble model cluster analysis continues to
depict a variable solution space that's mainly focused around how
fast the troughing and ridging come through the western United
States.
Coastal flooding concerns continue across Bayshore locations within
the San Pablo, San Francisco, and Monterey Bays and the Pacific
coastal regions through Friday. At the San Francisco tidal gauge,
high tide is expected to be 1.9 ft above normal (7.7 ft MLLW) at
12:56 PM Wednesday 10/28, 1.7 ft above normal (7.5 ft MLLW) at
01:43 PM Thursday 10/29, 1.6 ft above normal (7.4 ft MLLW) at 02:39
PM Friday 10/30, and 1.0 feet above normal (6.8 ft MLLW) at 03:44
PM on Saturday 10/31, including around 1.2 ft of surge residual
partially attributed to impacts from El Nino.
&&
.AVIATION...
(12Z TAFS)
Issued at 439 AM PDT Tue Oct 27 2026
Scattered cumulus clouds are bringing passing VFR to high MVFR
ceilings to the terminals this morning. Skies are more clear in
the North Bay, which has allowed enhanced radiational cooling,
and some patchy fog is being reported at both STS and APC. This
fog will clear by 18Z, with widespread VFR conditions expected
through the rest of the day as high clouds roll in. Boundary layer
winds are from the NW, with moderate strength expected through the
day.
Vicinity of SFO...Currently VFR with a 3,800' ceiling. There is a
high (90%) chance VFR conditions persist through the morning and
it's nearly certain they will hold through the afternoon. WNW
winds ramped up early this morning, and will remain moderate to
strong through the day.
SFO Bridge Approach...While ceilings are above 3,000' at SFO and
San Mateo Bridge, they are less than 4,000' at Palo Alto and
similar ceilings could impact San Jose at any time. These
approach clouds should clear between 20-22Z.
Monterey Bay Terminals... Both SNS and MRY are expected to hold on
to VFR conditions through the day, but there is a large cloud bank
east of SNS that could bring VFR ceilings this morning. Otherwise
winds will be diurnally driven, with moderate strength in the
afternoon.
&&
.MARINE...
(Today through Sunday)
Issued at 439 AM PDT Tue Oct 27 2026
Buoys are reporting a fresh NW breeze across the coastal waters
this morning. Winds will increase to a strong breeze by this
afternoon, building rough seas across exposed waters. Conditions
will gradually start to improve Thursday as winds decrease to and
seas subside.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory until 5 PM PDT Friday for CAZ006-505-506-
508-509-529-530.
PZ...Small Craft Advisory until 9 PM PDT this evening for Pt Arena to
Pt Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.
Small Craft Advisory from 3 PM to 9 PM PDT Wednesday for Pigeon
Pt to Pt Pinos 0-10 nm-Pt Arena to Pt Reyes 0-10 nm-Pt
Pinos to Pt Piedras Blancas 0-10 nm.
Small Craft Advisory until 9 PM PDT Wednesday for Pt Arena to Pt
Reyes 10-60 NM.
Small Craft Advisory from 9 AM this morning to 9 PM PDT
Wednesday for Pigeon Pt to Pt Pinos 10-60 NM.
&&
$$
SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Flynn
MARINE...Flynn
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Prepared by Boulder-Creek.com Weather at: Tue Oct 27 06:30:04 PDT 2026
From the National Weather Service
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