Tamal, California Weather Forecast Discussion

346
FXUS66 KMTR 032044
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
144 PM PDT Fri Oct 3 2025
...New SHORT TERM...
.KEY MESSAGES...
Updated at 143 PM PDT Fri Oct 3 2025
- A slight chance for showers and isolated thunderstorms across
   the North Bay and East Bay this afternoon
- Strong northwesterly winds continue through this evening,
   particularly along the coast and across higher elevations
- Warmer and drier this weekend, with moderate offshore wind
   expected from Saturday - Tuesday in the higher elevations
&&
.SHORT TERM...
Issued at 143 PM PDT Fri Oct 3 2025
(This evening through Saturday)
Isolated rain showers linger over the southern coastal waters and
the Central Coast this afternoon. However, they appear to be
diminishing in coverage as the main mid/upper level low pressure
shifts towards Nevada. Temperatures this afternoon be cool, warming
only into the lower 60s near the coast to lower 70s inland. Surface
based cape will increase with daytime heating to around 100-300 J/kg
and PWAT values around 0.80" this afternoon across the North Bay and
interior East Bay before diminishing after sunset. Thus, rain shower
chances, and a non-zero chance for isolated thunderstorm will
continue across the aforementioned areas through this evening.
As the low pressure shifts further inland into the Intermountain
West, northwesterly winds will increase through this evening and
again on Saturday afternoon and evening. This will result in a
drying trend into the upcoming week. Thus, temperatures will drop to
or just below seasonal averages.
&&
.LONG TERM...
Issued at 1208 AM PDT Fri Oct 3 2025
(Saturday night through Thursday)
While the weather will remain nice with seasonal temperatures and
sunny afternoons through the weekend, the pattern will gradually
evolve. As the deep trough that was responsible for our disturbed
weather this week slides west of the Rocky Mountains by late
Saturday, high surface pressure will build in its wake. Meanwhile,
a weak thermal trough will develop over the Central Valley and
get nudged to the coast by a 500 mb cut-off low over the NE
Pacific. This will flip the pressure gradient and cause winds to
shift from the typical NW to an offshore N or NE direction
starting as early as late Saturday. The PGE-WRF ensemble SFO-WMC
gradient envelope bottoms out anywhere from -4 mb to -9 mb on
Monday morning. While it still looks like a moderate strength
event, the forecast trend has been gradually increasing this
gradient. Offshore winds in October can bring fire weather
concerns, but the moderate speed and recent wet weather are
mitigating factors this time. Outside of fire weather concerns, offshore
winds this time of year tend to bring really nice weather to the
Bay Area and Central Coast with warm temperatures and clear
skies.
After the offshore winds die down, another cold front is likely
late next week. GEFS IVT ensemble members all stay below 250 kg/ms
with no chance of rain through Thursday, but longer range
guidance hints that more substantial rain is possible by Friday.
4/50 ECMWF ensemble members show Santa Rosa receiving over 1" of
rain in 24 hours, with the ensemble mean near 0.25" on an
increasing trend. There is still a lot timing and intensity
uncertainty with this pattern, and a few members (18, 38, 39, 48)
don`t develop the coastal low pressure system at all and stay
totally dry next weekend.
&&
.AVIATION...
(18Z TAFS)
Issued at 1051 AM PDT Fri Oct 3 2025
Patchy MVFR stratus will pester a handful of the terminals today
with most sites VFR at or after 21 UTC this afternoon. There`s a
potential for SHRA INVOF of North Bay terminals later this
afternoon and this may translate to a threat for surface wind
shifts and turbulence below FL050. MVFR cigs are forecast to
return overnight into Saturday morning at KHAF and the immediate
Bay Area terminals, though confidence is low. VFR will return late
Saturday morning and into the afternoon hours.
Vicinity of SFO...Intermittent MVFR stratus is forecast to
persist through 20 UTC. Confidence in timing of clearing is low as
stratus has largely lingered longer than initially anticipated. Impacts
from morning cigs may linger into the early afternoon. W to NW
winds will funnel through the San Bruno Gap and with gusts as
great as 25 knots. VFR is anticipated for this evening, though
there is a non-zero chance for cigs around FL040-FL050 to continue.
Thereafter, the next best chance for MVFR cigs is just after
sunrise Saturday, though confidence is low given mixed signals
from model guidance. For now, I`ll advertise intermittent cigs
near FL015 from 1200-1600 UTC with VFR thereafter.
SFO Bridge Approach...Cigs near FL020 through 20 UTC with VAPS
anticipated thereafter. However, there remains a 20-30% chance
that cigs below FL040 persist. VAPS probable for the evening
push, with intermittent cigs around 1200 UTC Saturday.
Monterey Bay Terminals...Radar indicates a few returns across
Monterey Bay and I`ve inserted a few hours of VCSH. Intermittent
MVFR cigs are forecast to also persist through mid-afternoon.
Confidence is high in a window for VFR, but there is a signal for
a return of MVFR as early as 03 UTC. This portion of the TAF will
be fine tuned as we roll through the day, but there does appear to
be a 60-70% chance for overnight MVFR cigs with VFR returning
after 17 UTC Saturday.
&&
.MARINE...
(Today through Wednesday)
Issued at 910 AM PDT Fri Oct 3 2025
A few scattered showers will continue through the day today.
Fresh to gale force breezes are forecast, especially for outer
waters near and north of Pigeon Point this afternoon and into the
pre-dawn hours on Saturday. This will translate to steep and rough
seas up to 10 feet resulting in hazardous boating conditions. Winds
abate after through sunrise Saturday, however, fresh to near gale-
force northerly winds resume Saturday afternoon. Winds and seas
ease next week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Saturday for Mry Bay-Pigeon
     Pt to Pt Pinos 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.
Small Craft Advisory until 3 AM PDT Sunday for Pigeon Pt to Pt
     Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Pinos to Pt
     Piedras Blancas 0-10 nm.
Small Craft Advisory until 3 PM PDT this afternoon for Pt Arena
     to Pt Reyes 10-60 NM.
Small Craft Advisory from 3 AM Saturday to 3 AM PDT Sunday for
     Pt Arena to Pt Reyes 10-60 NM.
Gale Warning until 3 AM PDT Saturday for Pt Arena to Pt Reyes 10-
     60 NM.
&&
$$
SHORT TERM...RGass
LONG TERM....Flynn
AVIATION...Bain
MARINE...Bain
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NWS MTR Office Area Forecast Discussion