FXUS66 KMTR 291148
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
448 AM PDT Thu Oct 29 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 1203 AM PDT Thu Oct 29 2026
- Moderate coastal flooding at high tide for Bayshore and Pacific
Coast locations through Friday and Saturday
- Seasonal to slightly below seasonal temperatures through the
extended forecast
- Potential for rain this weekend and again early to mid next
week
&&
.SHORT TERM...
Issued at 1203 AM PDT Thu Oct 29 2026
(Today and tonight)
Satellite imagery shows high clouds across the region, the byproduct
of a decaying upper level low from the west that is merging into the
troughing pattern across the West Coast. Cloudy conditions will
likely persist through the day today as morning lows hover in the
lower to middle 40s in the inland valleys and the upper 40s to the
lower 50s closer to the coasts, while highs remain in the upper 60s
to the lower 70s in the inland valleys and the SF Bayshore and the
lower to middle 60s along the Pacific coast. Winds will generally
remain light and gentle with some breeziness in the afternoon and
evening hours in favored locations.
Now to address the elephant in the room. Several high-resolution
models, including the HRRR and the experimental RRFS, are showing
some simulated reflectivity returns coming in later this morning and
continuing through the day across the region, but especially focused
on the South Bay and the Central Coast. On the surface it seems like
rain should be in the forecast, but other meteorological analysis
comes in and says "Not so fast!". Looking at the 00Z (5 PM PDT)
sounding from Oakland reveals a deep layer of very dry air
stretching from the 850 mb layer to the 500 mb layer where dew
points range from around -30 to -50 degrees Centigrade. That is a
three-mile thick column of air that any potential precipitation will
have to overcome for rain to develop, and whether we'll get anything
making it to the surface depends on whether developing cells can
overcome that dry layer. The current forecast leans towards "no"
with anything seen on KMUX radar today evaporating before it reaches
the ground, or virga. We can't dismiss the possibility of rain
completely, but it looks to be something that at most brings a few
sprinkles or hundredths of an inch of rain to the mountaintops over
something that would be more impactful.
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 1.9 ft above normal (7.7 ft MLLW)
at 01:43 PM Thursday 10/29, including around 1.2 ft of surge
residual partially attributed to impacts from El Nino.
&&
.LONG TERM...
Issued at 1203 AM PDT Thu Oct 29 2026
(Friday through Wednesday)
High temperatures in the inland valleys will fluctuate in the middle
60s to the lower 70s through the seven day outlook. Large scale
troughing remains in place through the next couple days before
chances for rain come into the region later on Saturday into Sunday.
As the trough starts to push its way eastwards into the West Coast,
a upper level jet streak will take aim at the central and southern
portions of California. This will facilitate cyclogenesis and a
developing surface low takes aim at southern California and the
northern portions of Baja California. Those regions will see the
bulk of the rain from this system, but the fringes of the moisture
will come into the Central Coast and will likely give the interior
measurable rain, if not much rain. Forecast rain totals are still
fluctuating, but the interior portions of Monterey and San Benito
Counties should see around a tenth to a third of an inch of rain
Saturday into early Sunday. Elsewhere, light showers are possible
within the Monterey Bay region and even extending into the South
Bay, especially if the parent system takes a more northerly track.
A progressive ridge will come into the region Sunday into Monday
before another system comes in towards the end of the seven-day
outlook. Last time I had stated that the speed and track of that
incoming system was highly uncertain. That remains the case judging
from the ensemble model cluster analysis and even just looking at
various model outputs heading into the middle of next week. The
current forecast retains the rain chances for the end of the seven-
day outlook, but by necessity they are low (10-30% probability) and
the certainty in any further detail is lower still.
Coastal flooding concerns continue across Bayshore locations within
the San Pablo, San Francisco, and Monterey Bays through Saturday and
the Pacific coastal regions through Friday. At the San Francisco
tidal gauge, high tide is expected to be 1.6 ft above normal (7.4 ft
MLLW) at 02:39 PM Friday 10/30, and 1.1 feet above normal (6.9 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 444 AM PDT Thu Oct 29 2026
VFR. Weak offshore flow continues this morning with a gradual
shift to weak onshore flow later today and tonight. The marine
layer will still struggle to reorganize through the forecast
period with a slight chance of MVFR ceilings developing tonight
into early Friday morning.
Vicinity of SFO...VFR. As mentioned above, weak offshore flow will
continue through this morning before a gradual shift to onshore
flow by later today and tonight.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR. Weak onshore flow develops this
afternoon with a slight chance of MVFR ceilings returning early
this evening into Friday morning.
&&
.MARINE...
(Today through Tuesday)
Issued at 444 AM PDT Thu Oct 29 2026
Conditions gradually improve today with strong northwest breezes
becoming fresh to moderate with rough seas improving as well.
Improving conditions will continue into the weekend while a long
period west-northwest swell arrives this weekend and continues
into next week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory until 6 PM PDT Saturday for CAZ006-506-
508-529-530.
Coastal Flood Advisory until 5 PM PDT Friday for CAZ505-509.
PZ...Small Craft Advisory until 9 PM PDT this evening for Pt Arena to
Pt Reyes 10-60 NM.
Small Craft Advisory until 3 PM PDT this afternoon for Pigeon Pt
to Pt Pinos 10-60 NM.
&&
$$
SHORT TERM...DialH
LONG TERM....DialH
AVIATION...JM
MARINE...JM
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Prepared by Boulder-Creek.com Weather at: Thu Oct 29 08:30:03 PDT 2026
From the National Weather Service
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