FXUS66 KMTR 292009
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
109 PM PDT Thu Oct 29 2026
...New SHORT TERM, LONG TERM...
.KEY MESSAGES...
Updated at 107 PM PDT Thu Oct 29 2026
- Moderate coastal flooding at high tide for Bayshore and Pacific
Coast locations through Friday; coastal flooding continues for
Bayshore locations on Saturday
- Seasonal to slightly below normal temperatures through the
extended forecast
- Potential for rain this weekend
&&
.SHORT TERM...
Issued at 107 PM PDT Thu Oct 29 2026
(This evening through Friday night)
A deep upper level trough originating from the Gulf of Alaska will
continue to move into the West Coast through the weekend. It will
bring an influx of colder air that continues to keep our
temperatures below normal through the extended forecast. Did you
feel a chill in the air this morning? North Bay residents saw the
coolest temperatures with lows dropping into the upper 30s/low 40s
across the interior Valleys. Expect cooler morning conditions to
continue Thursday night into Friday morning as highs drop in the 40s
across the North Bay and low to mid 50s across the rest of the Bay
Area and Central Coast. High temperatures on Friday will be in the
60s across the region with upper 50s to low 60s directly along the
coast.
High resolution guidance does show some potential for light rain
tonight into Friday but confidence is on the lower end. KMUX
continues to show some light radar echoes in the Central Coast with
nothing across the Bay Area. If we were to see showers they would be
most likely over the Central Coast, where the best moisture
currently is, while the Bay Area stays dry. Another factor to
consider is where in the atmosphere the moisture is. Model guidance
suggests the primary moisture source is high level which means any
showers that do develop today will be high based. Which means, given
the large dry lair precipitation must fall through to reach the
surface, it is likely that any falling precipitation will evaporate
before reaching the ground (virga). While noticeable rain is
unlikely, we can expect to see a return of low level clouds
overnight as additional low level moisture begins to arrive with the
more unsettled weather.
The Coastal Flood Advisory continues Thursday and Friday with up to
1.9 ft of inundation above ground level expected today (10/29)
within +/- 90 minutes of high tide (1:43 PM). Tidal heights are
expected to trend downwards through the remainder of the week with
up to 1.6 ft of inundation above ground level possible on 10/30 with
high tide occuring at 2:39 PM. The caveat to this is that tidal
anomalies have not been decreasing as rapidly as initially thought
that they would which necessitated the advisory being expanded into
Friday and Saturday. So although the current advisory expires on
Saturday, there is still the potential for the advisory to be
expanded into Sunday if the anomaly continues to trend downwards
slower than anticipated.&&
.LONG TERM...
Issued at 107 PM PDT Thu Oct 29 2026
(Saturday through next Wednesday)
Upper level troughing will become more pronounced across the West
Coast Saturday and Sunday. Guidance shows a few areas of weak low
pressure developing offshore of the PNW and offshore of Northern
California. A slightly stronger area of low pressure is located to
the southwest of Southern California and will strengthen into a weak
low pressure system as it moves towards the California-Mexico
border. This system is associated with a much more impressive
moisture transport that will move into Southern California with the
tail edge of the moisture just tapping the Central Coast and Bay
Area. The current forecast shows minimal rain across our forecast
area with only a few hundredths of an inch expected. The exception
would be the North Bay Coastal Mountains and the interior Central
Coast where between a tenth to a quarter of an inch is expected. For
the North Bay Coastal Mountains, orographic uplift is likely
responsible for the slightly higher totals. The Interior Central
Coast benefits both from orographic uplift along the Gabilan range
and from being closer to the primary moisture plume over Southern
California. The previous shift noted that precipitation values for
this weekend have been flipping around which is still partially
true. Up until this morning's forecast update, the values had been
trending downwards. However, models are now keying in on the
moisture plume spreading more northwards and ensembles show the
potential for a trace of rain to a tenth of an inch. This is
consistent with the current forecast and there is good consensus
between the ECMWF and GFS that precipitation will be light. Showers
are likely to develop early Saturday morning across the interior
Central Coast and spread northwards into the Bay Area by late
Saturday. Light rain/drizzle may start during prime Trick or
Treating hours but the highest chances for precipitation will fall
after midnight/early Sunday morning. There is a low (< 15%) chance
of thunderstorms on Saturday/Sunday as this system moves through.
The overall environment looks fairly marginal but the upper level
low is transporting a cold enough airmass in that it may be enough
to bring localized thunderstorms to the higher elevations. The best
potential is over the marine environment and along the coastline
with much lower chances across the interior.
Below normal temperatures continue this weekend into next week as
the upper level trough brings another round of much colder air into
the region. The 850 mb temperature looks to drop to between 4-6 C
this weekend which is below the 25% percentile of 850 mb
temperatures for late October. As a result, high temperatures will
be well below average on Saturday in the upper 50s to low 60s. We
can expect temperatures to gradually warm up heading into next week
as the trough moves out and upper level ridging rebuilds across the
region. This would see temperatures warming back into the upper 60s
to low 70s across the interior while coastal areas stay in the upper
50s to 60s. The most recent forecast update has pushed our next rain
episode back from mid next week to late next week. Ridging is now
expected to persist through the first part of the week with the next
trough not set to arrive until Wednesday/Thursday. It's too far out
to talk about rain totals for this event but it will definitely be
something to keep an eye on.
Coastal flooding concerns continue across Bayshore locations within
the San Pablo, San Francisco, and Monterey Bays through Saturday. At
the San Francisco tidal gauge, high tide is expected to be 1.1 feet
above normal (6.9 ft MLLW) at 03:44 PM on Saturday 10/31.
&&
.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...Kennedy
LONG TERM....Kennedy
AVIATION...RGass
MARINE...RGass
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Prepared by Boulder-Creek.com Weather at: Thu Oct 29 14:30:03 PDT 2026
From the National Weather Service
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