Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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FXUS66 KMTR 140938
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
238 AM PDT Tue Oct 14 2025

...New SHORT TERM, LONG TERM...

.KEY MESSAGES...
Updated at 236 AM PDT Tue Oct 14 2025

 - Post-frontal rain showers and up to a 15% chance for
   thunderstorms today

 - Warming and drying trend Wednesday through Saturday

 - Unsettled weather returns Sunday

&&

.SHORT TERM...
Issued at 236 AM PDT Tue Oct 14 2025
(Today and tonight)

All signs point to rain shower/thunderstorm activity declining
through the day as the surface low pressure system and it`s
attendant cold front (as well as it`s mid-to-upper level support)
will weaken and exit the region through the day. There will still be
chances for rain showers and thunderstorms until the features exit
around midnight. Let`s take a deep dive into the thunderstorm
potential for today by addressing the critical ingredients of lift,
instability, and moisture. In addition to what has already been
discussed lift wise, a 95 knot jet streak from a dive in the Polar
Jet Stream will shift into our region today, which could allow for
more ascent. Instability will be characterized by low CAPE (500
Joules/kilogram) and conditionally unstable lapse rates (7 degrees
Celsius/kilometer). Moisture will ebb and flow throughout the day
and will be highly dependent upon the placement of the surface low
pressure system. A solution over the water will be more moist than a
solution inland which will be capable of entraining drier air into
the system. With similar ingredients on tap for today as what was
present yesterday, I would be very surprised if today outperformed
yesterday given the very limited amount of lightning that was
observed. The best chances for thunderstorms (up to 15%) are for
Southern Monterey and San Benito Counties and the adjacent waters.
Thunderstorm or not, cells will still be capable of producing
locally heavy rainfall resulting in nuisance/urban flooding,
erratic/gusty winds, small hail, and waterspouts. Caution should
continue to be exercised through the day when driving. Roads will
still be wet for this morning`s commute so please allow extra
patience, space, and time when driving, especially for super
commuters who will undoubtedly be driving in the dark. Remember:
turn around, don`t drown! This system is also a cold one. Calm,
clear, and cold conditions tonight will yield near-freezing
temperatures for far interior Monterey and San Benito Counties east
of Highway 101. In addition to the aforementioned near-freezing
temperatures, patchy frost will be possible in sheltered locations
east of Highway 101 in Monterey and San Benito Counties. While
there`s not great consensus amongst guidance/models, the potential
will be there for fog to develop tonight. The limiting factor will
likely be cloud cover as it would allow for less efficient radiative
cooling.

&&

.LONG TERM...
Issued at 236 AM PDT Tue Oct 14 2025
(Wednesday through Monday)

Global ensemble clusters are in agreement that upper-level shortwave
ridging will nose in from the Eastern Pacific Ocean by Wednesday. At
the surface, high pressure will also nose in from the Eastern
Pacific Ocean and build into the Pacific Northwest through Thursday.
This will translate to a northerly (drying) gradient developing
across California. By Friday and into Saturday, the high pressure
builds into the Great Basin while a coastal trough develops off the
coast of California. This will result in light offshore flow for
these two days. Fortunately, just coming off the heels of a
widespread wetting rain event, this warming and drying trend will
not be a fire weather concern. Global ensemble clusters are in
agreement that heights will fall Sunday with an approaching upper-
level longwave trough. Confidence quickly plummets by Monday as
there is near split percentages on if troughing will continue to dig
into the region or if high pressure will rebuild. Nonetheless, at
least expect an increase in cloud cover and wind towards the end of
the forecast. While the current forecast is dry, there is potential
for rain returning to the forecast with ECMWF and GFS total
precipitation ensemble spread showing a three inch disparity.

&&

.AVIATION...
(06Z TAFS)
Issued at 955 PM PDT Mon Oct 13 2025

The main frontal band of rain, and its attendant reduced
visibilities and gusty winds, has moved into the interior portions
of the Bay Area but is still making its way through the Central
Coast. Overnight, winds will generally be light and mostly driven by
local effects, with generally VFR conditions with mid-level ceilings
possible. A chance for scattered showers and isolated thunderstorms
continues across the region through Tuesday with reduced
visibilities and gusty winds expected within and near the
thunderstorm cells. In addition, the North Bay could see steadier
light rain from the backside of the frontal system through Tuesday
morning. Otherwise, afternoon winds will be muted on Tuesday with
hints of a weak onshore flow within the models. In the post-frontal
environment, ceilings are tricky to forecast, but indications point
to generally VFR conditions with mid-level ceilings outside of the
strongest storms, barring the North Bay where MVFR ceilings could
accompany the steady rain.

Vicinity of SFO... Moderate confidence of VFR with mid-level
ceilings through the TAF period. Chance for scattered showers with
isolated thunderstorms continues through Tuesday morning, with the
main impacts being reduced visibilities and gusty winds if one
develops over the terminal. Otherwise winds will be weakly onshore
with gusts reaching 8 kt. Some divergence in the model outputs
towards the end of the TAF period with some high resolution models
pointing to southerly winds Tuesday night.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... The main rain band is expected to push out
of the terminal areas within the next couple of hours. VFR with mid-
level ceilings persists through the TAF period with light drainage
winds overnight followed by breezy west winds Tuesday afternoon.
Isolated showers and thunderstorms are possible through Tuesday
morning with the main impacts being reduced visibilities and
gusty winds if one forms or moves over a terminal.

&&

.MARINE...
(Tonight through next Sunday)
Issued at 845 PM PDT Mon Oct 13 2025

The strongest winds and heaviest rains have moved inland, but a
chance for showers and isolated thunderstorms persists through
Tuesday morning. The showers will become more isolated while the
winds decrease overall. Rough seas to 10 feet will persist into
Wednesday, then becoming moderate through late Thursday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
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...Sarment
LONG TERM....Sarment
AVIATION...DialH
MARINE...DialH

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