FXUS66 KMTR 010014
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
514 PM PDT Mon Aug 31 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 1250 PM PDT Mon Aug 31 2026
- Well below normal temperatures through Friday, gradual warming
and drying trend this weekend
- Beneficial wetting rain in the North Bay Tuesday through
Thursday, drizzle/light rain possible elsewhere
&&
.SHORT TERM...
Issued at 1250 PM PDT Mon Aug 31 2026
(Monday through Friday)
Upper-level shortwave troughing will swing into Northern California
tomorrow; this will result in temperatures well below normal, a
chance for drizzle/light rain, and widespread cloud cover. The best
chances for drizzle/light rain will be in the North Bay,
particularly along the coast and in the higher terrain with the help
of orographic lift. A reinforcing upper-level low and an attendant
cold front will approach the area Wednesday into Thursday. This will
keep well below normal temperatures and cloudy conditions around and
likely make the marine layer arbitrary. There will be a better
chance for drizzle/light rain with this round with a lifting
mechanism in place as PWAT climbs to near one inch (90th
percentile). It is likely (60+% chance) that the northwestern half
of the North Bay gets wetting rain (0.10 inches) between now and
then. While rainfall is expected to be beneficial, wet roadways will
create slick driving conditions and increase stopping distance.
&&
.LONG TERM...
Issued at 1250 PM PDT Mon Aug 31 2026
(Saturday through Sunday)
Global ensemble clusters diverge on solutions dramatically going
into the weekend, specifically on low vs trough and the location and
timing of the feature, so basically everything. What is certain is
that the region will be under the influence of some kind of
troughing through the weekend. As it weakens through the weekend, a
gradual warming and drying trend will commence with temperatures
moderating to slightly below to near normal. Beyond the seven day
forecast and into Labor Day/early next week, Invest EP95 well
offshore of Southwestern Mexico becomes a variable. Uncertainty over
the weekend will compound and propagate into the tropical side of
the forecast, making it impossible to talk specific impacts at this
point in time. The primary impacts would likely be rain and wind
with impacts likely decreasing from south to north.
&&
.AVIATION...
(00Z TAFS)
Issued at 514 PM PDT Mon Aug 31 2026
VFR everywhere expect for HAF, SFO, and OAK where MVFR ceilings
prevail. Marine stratus is expected to make another push this
evening with MVFR ceilings developing at most terminals during the
post-sunset hours and overnight. Low to medium confidence on the
onset times for MVFR ceilings given the current stratus feed over
the ocean is rather disorganized. Diurnal onshore winds persist
through the TAF period with APC and LVK continuing to experience
gusts around 20 kt this evening. Stratus is expected to scatter out
late tomorrow morning into the early afternoon.
Vicinity of SFO...MVFR ceilings prevail through Tuesday morning with
moderate onshore breezes. Stratus coverage may intermittently become
VFR this afternoon, but should become solid MVFR around sunset time.
Leaned on an optimistic clearing time for Tuesday morning, though
confidence is low.
SFO Bridge Approach...Patchy stratus coverage is expected to
continue into the evening. Otherwise, similar to SFO.
Monterey Bay Terminals...VFR is anticipated through the early
evening hours before marine stratus re-develops. Forecast confidence
is low to medium as the current satellite presentation of stratus is
very disorganized. At this time, the expectation is that stratus
will invade KMRY just after sunset this evening, with MVFR arriving
a few hours after that at KSNS. While IFR is a possibility, the
current TAF set leans on a more optimistic ceiling forecast given
the amount of dry air likely just above the marine layer. Otherwise,
diurnal breezes with speeds of 8-12 knots are advertised throughout
the TAF cycle.
&&
.MARINE...
(Tonight through next Sunday)
Issued at 514 PM PDT Mon Aug 31 2026
Northwest to westerly gentle breezes will persist through the
week with intermittent periods of moderate breezes. Wind driven
seas are anticipated to remain slight to moderate through the
week with long period southerly swell persisting thanks to
tropical cyclone activity.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Tuesday for SF Bay N of Bay
Bridge.
Small Craft Advisory until 9 PM PDT this evening for Mry Bay.
&&
$$
SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...Navarrete/Bain
MARINE...Bain
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Prepared by Boulder-Creek.com Weather at: Mon Aug 31 18:30:03 PDT 2026
From the National Weather Service
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