FXUS66 KMTR 271814
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1114 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...
(18Z TAFS)
Issued at 1114 AM PDT Tue Oct 27 2026

VFR conditions are expected for the TAF cycle, with the marine layer 
essentially being non-existant. The main challenges will be any 
cumulus or stratocu that develop, similar to what we are seeing from 
roughly the East Bay and San Mateo County into the northern portion 
of the Central Coast. Sites that are seeing cigs from these clouds 
are reporting values between FEW or SCT025-035, perhaps some rogue 
BKN at times. Any of those BKN025 or BKN030 cigs should be short 
lived or temporary. The only other forecast challenge for tonight, 
is if KSTS gets any radiational fog/stratus again. Opted to hint at 
it with what has happened the past two mornings, but confidence was 
too low to lock in LIFR conditions. 

Vicinity of SFO...Some cumulus is popping up around SF Bay and 
generally appears to be tied to the terrain. Expecting VFR conditions 
to prevail through the period, with the onshore winds picking up t 
his afternoon. Sustained speeds should be around 12-15kt during the 
peak, with gusts up to 20-25kt possible. Winds begin to ease later 
in the evening, but will become breezy again mid to late Wednesday 
afternoon. 

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Satellite imagery is most interesting over 
the northern portion of the Central coast where we have a mix of 
stratus and stratocu being observed. TAF sites remain VFR here and 
are reporting mainly OVC cigs around 035-040. Models aren't really 
depicting this too well and with stratus kind of back filling from 
the northwest, current thinking is we should remain cloudy through 
the afternoon. If the clouds hold, we could still see BKN VFR cigs 
into the early evening. Offshore flow returns to these terminals 
tonight, which should clear out any lingering cloud should they 
still exist. 

&&

.MARINE...
(Today through Sunday)
Issued at 1114 AM PDT Tue Oct 27 2026

Fresh NW breezes and strong gusts are being observed 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 Pigeon Pt to 
     Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...KR
MARINE...KR

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Prepared by Boulder-Creek.com Weather at: Tue Oct 27 12:30:04 PDT 2026