FXUS66 KMTR 291746
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
1046 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...
(18Z TAFS)
Issued at 1044 AM PDT Thu Oct 29 2026
High clouds continue to stream overhead with ceilings between
15kft and 25kft and will likely lower to around 10kft late this
evening and into Friday morning. Onshore winds will increase once
again by late morning and especially so by this afternoon and into
the early evening. Winds diminish overnight and into Friday
morning. Onshore winds increase once again by Friday afternoon.
Vicinity of SFO...VFR through the TAF period. Onshore winds
increase by early afternoon and persist through the late evening
before diminishing and become light/variable Friday morning. There
is less than a 20% probability for MVFR ceilings to develop
across the Bay Area terminals early Friday morning.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR through the TAF period. Onshore
winds return later this morning and prevail through sunset this
evening. KSNS is currently experiencing (southeasterly) drainage
winds that are forecast to return onshore by early afternoon.
There is a 15-30% probability for MVFR ceilings to develop late
this evening and into Friday morning, yet the lack of a marine
layer and high cloud cover is forecast to limit this potential.
&&
.MARINE...
(Today through Tuesday)
Issued at 1044 AM PDT Thu Oct 29 2026
Conditions gradually improve through the day 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 3 PM PDT this afternoon for Pigeon Pt
to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM.
&&
$$
SHORT TERM...DialH
LONG TERM....DialH
AVIATION...RGass
MARINE...RGass
Visit us at www.weather.gov/sanfrancisco
Follow us on Facebook, X, and YouTube at:
www.facebook.com/nwsbayarea
x.com/nwsbayarea
www.youtube.com/nwsbayarea
Prepared by Boulder-Creek.com Weather at: Thu Oct 29 12:30:04 PDT 2026
From the National Weather Service
|