421
FXUS66 KMTR 290424
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
924 PM PDT Thu Aug 28 2025

...New AVIATION...

.KEY MESSAGES...
Updated at 239 PM PDT Thu Aug 28 2025

 - Near normal temperatures today and Friday, warmer for the
   weekend and beyond

 - Elevated fire weather concerns across interior mountains this
   weekend with low RH and moderate onshore winds in the afternoon

 - Hazardous coastal conditions from Saturday - Tuesday due to
   long period southerly swell

&&

.UPDATE...
Issued at 715 PM PDT Thu Aug 28 2025

While the weather pattern could be described as "quiet", there are
some hazards to be aware of this holiday weekend. First is the
heat. With a compressed marine layer and 850 temps near 25C,
temperatures will be anywhere from 5-10 degrees above normal.
Remember that we are in the warmest time of the year, so anything
above normal will bring some impacts. Most interior areas are
under moderate HeatRisk this weekend, with minor risk closer to
the coast. With 850 mb temperatures near 25C, there will be a
strong inversion overnight and limited cooling in the hills. This
heat will also lower the relative humidity. While the winds are
generally moderate and onshore, the standard afternoon breeze will
be enough to bring elevated fire weather concerns. We`re focused
mainly on the East Bay hills, where the winds will be strongest in
the gaps and passes. Finally, incoming long-period SSW swell from
Tropical Storm Juliette will bring hazardous beach conditions
from Saturday through Tuesday. Hazards include sneaker waves, rip
currents and rough surf. With warm weather and a long weekend,
more people will head to the beach, increasing the exposed to this
danger.

&&

.SHORT TERM...
Issued at 239 PM PDT Thu Aug 28 2025
(This evening through Friday)

While there has bean a lot of activity for our friends in the
southernmost portions of the state, the Bay Area and Central Coast
has had a fairly easy-going day. Cloud cover has retreated to the
edge of the outer marine zones and temperatures are continuing to
rise with the clear skies. Expect highs in the mid to upper 60s
along the coast, 70s and 80s for inland areas, and a few 90s for the
far interior. Which is fairly close to average for this time of year
across the board.

Cloud cover will be slow to return tonight, allowing for some fair
initial cooling. Cloud cover does look to make a strong return
overnight, but the slight compressing of the marine layer will limit

&&

.LONG TERM...
Issued at 239 PM PDT Thu Aug 28 2025
(Friday night through next Wednesday)

Speaking of the marine layer compressing, it will continue to do so
into the weekend. Our mostly neutral upper level pattern turns to a
slight ridging pattern into the weekend, compressing the marine
layer, and causing a warming and drying trend. The far interior will
see poor humidity retentions and recoveries, along with temperatures
breaking into the 100s and lows warming into the 60s (and 70s for
higher peaks). The immediate coast and adjacent valleys will have a
compressed, yet still intact marine layer preventing from too much
of a warm up. However, the areas currently seeing the marine
influence that look to lose that influence over over the weekend
will see the larges jumps in temperatures, trending 5 to 10 degrees
warmer than today.

The longer-term forecast has fair agreement across models into the
next work week, with some slight cooling for Monday as the ridge
relaxes slightly. This will allow for slight increases in onshore
flow, but the interior looks to stay warm and dry. Models struggle
to show anything truly breaking the ridge pattern through the next
work week, and even hint at additional warming in the mid week and a
plateauing of temperatures into the next weekend. This suggests some
potential for prolonged heat affecting the area, and only modest
cooling after the ridge pattern slowly resolves well into the long-
term forecast. This will be something to keep track of as the
forecast develops.

&&

.AVIATION...
(06Z TAFS)
Issued at 916 PM PDT Thu Aug 28 2025

Sharp marine layer expansion this evening which ideally would lead
to slightly higher CIGs and potentially coastal DZ overnight
tonight and into Friday morning. Later arrival for stratus than
previously anticipated, but confidence is still high that we will
see MVFR/IFR cigs across most terminals before sunrise Friday. A
deeper marine layer will also likely lead to a later clearing time
for some coastal and Bay Area terminals. Otherwise no surprises
expected regarding winds through Friday.

Vicinity of SFO...VFR going into the nighttime hours with moderate
confidence in timing of MVFR cigs Friday morning. Confidence is
higher that the terminal will see cigs to come extent around
sunrise Friday, but the time of arrival is less certain.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Later stratus arrival than previously
anticipated, but confidence is still high in MVFR cigs overnight
and into mid morning Friday. Coastal DZ also appears likely as the
marine layer deepens.

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 239 PM PDT Thu Aug 28 2025

Light winds and seas continue across the coastal waters through
the end of the week. Increasing wave heights and fresh to strong
gusts develop through the weekend, bringing hazardous conditions
across the coastal waters into next week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&

$$

SHORT TERM...Murdock
LONG TERM....Murdock
AVIATION...Behringer
MARINE...Behringer

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