FXUS66 KMTR 311109
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
409 AM PDT Sun Aug 31 2025
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 129 AM PDT Sun Aug 31 2025
- Moderate risk for heat-related illnesses today and Monday
- Elevated fire weather concerns across the interior mountains
into Monday with low RH and moderate onshore winds each
afternoon
- Hazardous coastal conditions through Monday night due to long
period southerly swell
&&
.SHORT TERM...
Issued at 129 AM PDT Sun Aug 31 2025
(Today and tonight)
Mostly clear skies will persist today and tonight. A drier airmass
combined with a compressed marine layer will result in spotty
stratus development confined to only the coastline, if there is any
at all. Temperatures will increase slightly for many locations this
afternoon from Saturdays highs. A Heat Advisory is not warranted,
but people visiting any of the numerous inland and elevated
recreational areas in our forecast area should be aware of the warm
temperatures and plan accordingly. Stay hydrated, seek shade, take
breaks and dont leave people or pets in vehicles. Breezy onshore
flow this afternoon will also result in elevated fire weather
concerns, see below for more information.
&&
.LONG TERM...
Issued at 129 AM PDT Sun Aug 31 2025
(Monday through Saturday)
A weak upper level low continues to gradually approach from
offshore. The weak disturbance will draw in improved mid-level
moisture between H50-H70. We will continue monitor the non-zero
chance for elevated convection Monday into Tuesday. As the upper
level disturbance approaches the coast, it is likely to evolve into
a negatively tilted open wave. As of right now, the best lift is out
of phase and north of the improving mid-level moisture that is
expected to be in place, however subtle changes in the timing and
position of the disturbance could lead to increasing chances of
elevated thunderstorms. Lightning and gusty winds would be the
primary concern. Beyond Tuesday, the moderate heat begins to ease
through mid-week, with notable cooling by the end of the week into
next weekend.
&&
.AVIATION...
(12Z TAFS)
Issued at 409 AM PDT Sun Aug 31 2025
VFR through the day. Breezy onshore winds develop this afternoon
with gusts at 15 to 20 knots, before diminishing this evening. High
resolution models are suggesting that stratus and fog return to the
immediate coastal region tonight through Monday morning. Confidence
on impacts to the terminals is moderate for HAF and MRY, and low
everywhere else.
Vicinity of SFO... VFR through the TAF period. Breezy west-northwest
winds develop this afternoon and evening gusting up to 25 knots
knots. A few high resolution models are suggesting that stratus
returns to the terminal area early Monday morning, but confidence is
very low.
SFO Bridge Approach... Similar to SFO.
Monterey Bay Terminals... VFR through the day with breezy onshore
winds developing this afternoon and evening. Moderate confidence
that stratus and fog return to the immediate coastal area and MRY
tonight, potentially extending beyond the end of the TAF period.
&&
.MARINE...
(Today through Friday)
Issued at 409 AM PDT Sun Aug 31 2025
Fresh to strong northwesterly breezes continue through the
weekend with strong gusts and thus hazardous conditions for small
craft across much of the waters. Moderate to fresh northwesterly
breezes will prevail Monday through Wednesday. Moderate seas
persist through Wednesday.
&&
.FIRE WEATHER...
Issued at 129 AM PDT Sun Aug 31 2025
Warm and dry conditions will continue today and Monday, especially
for locations above 500ft. Widespread MinRH values between 10%-20%
combined with occasional wind gusts up to 30 MPH will result in
elevated fire weather concerns. We are also monitoring the potential
for elevated thunderstorms Monday afternoon into Tuesday. Chances
are low at the moment, but if the pattern evolves with improved
timing of the mid-level moisture and best lift associated with the
upper level disturbance we could see some isolated convection across
portions of the Bay Area, East Bay Hills and North Bay.
&&
.BEACHES...
Issued at 939 PM PDT Sat Aug 30 2025
A Beach Hazards Statement is in effect through 11PM Monday due to
long period (18 seconds) southwesterly swell causing an increased
risk for sneaker waves and rip currents along southwest facing
beaches, including but not limited to: Stinson Beach, Santa Cruz
Boardwalk Beach, and Twin Lakes Beach. Sneaker waves can
unexpectedly run significantly farther up the beach than normal,
including over rocks and jetties. Rip currents are typically more
frequent and stronger in the vicinity of jetties, inlets, and piers.
It is always important, but especially so on a warm, dry, holiday
weekend, to exercise caution while at the beach. Never turn your
back on the ocean, remain out of the water to avoid hazardous
swimming conditions, keep pets on a leash, and wear a life jacket.
Sarment
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through Monday evening for CAZ505-509-
529.
PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this
evening for Mry Bay.
Small Craft Advisory until 9 PM PDT Monday for Pigeon Pt to Pt
Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm.
Small Craft Advisory from 3 PM this afternoon to 3 AM PDT Monday
for Pt Reyes to Pigeon Pt 0-10 nm.
Small Craft Advisory until 3 AM PDT Monday for Pigeon Pt to Pt
Pinos 0-10 nm.
Small Craft Advisory until 9 AM PDT Monday for Pt Pinos to Pt
Piedras Blancas 0-10 nm.
Small Craft Advisory until 3 AM PDT Tuesday for Pt Arena to Pt
Reyes 10-60 NM.
&&
$$
SHORT TERM...JM
LONG TERM....JM
AVIATION...DialH
MARINE...DialH
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Prepared by Boulder-Creek.com Weather at: Sun Aug 31 10:30:03 PDT 2025
From the National Weather Service
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