239
FXUS66 KMTR 261159
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
459 AM PDT Sat Jul 26 2025

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 153 AM PDT Sat Jul 26 2025

 - Below to near seasonal normal temperatures through Friday.

&&

.SHORT TERM...
Issued at 153 AM PDT Sat Jul 26 2025
(Today and tonight)

The July 26th 00Z sounding revealed an 850 millibar temperature of
17.15 degrees Celsius, just above the 25th percentile of 17.1
degrees Celsius for this date and time. San Jose (SJCthr) tied its
daily (July 25th) low maximum temperature record of 73 degrees
Fahrenheit set in 1924. Napa State Hospital (NSHC1) is forecast to
tie its daily (July 26th) low maximum temperature record of 70
degrees set in 1935. Needless to say widespread below normal
temperatures, a relatively deep marine layer, and drizzle will
continue today. The upper-level trough that has been the dictator of
our recent weather brings a low probability (5%) high-impact
scenario of elevated convection. The essential ingredients for
thunderstorms of lift, instability, and moisture are there, but they
are not impressive. With very little change to the pattern, it is
expected that convection will continue to present itself as it
has the previous two days, remaining confined to the north and
east of our region. If a thunderstorm were to develop, the primary
hazards will be dependent on if they are wet (rainfall greater
than or equal to 0.10 inch) or dry (rainfall less than 0.10 inch).
Wet thunderstorm hazards will be locally heavy rainfall and gusty
outflows while dry thunderstorm hazards will be new fire starts
and gusty outflows.

&&

.LONG TERM...
Issued at 153 AM PDT Sat Jul 26 2025
(Sunday through Friday)

Global ensemble clusters are in agreement of heights rising through
Tuesday as broad high pressure expands westward and a longwave ridge
is able to form over the Intermountain West. This will result in a
slight warming trend with temperatures returning to near normal for
valleys and terrain above the marine layer. While it is likely that
heights will begin to fall Wednesday as an embedded shortwave from
the upper-level low in the Gulf of Alaska traverses the region,
sensible weather will fluctuate very little through Friday with the
coast remaining cool, the interior remaining mild, and onshore flow
prevailing.

&&

.AVIATION...
(12Z TAFS)
Issued at 440 AM PDT Sat Jul 26 2025

The marine layer is 2,600 ft according to the ascending 12Z
weather balloon. With ceilings lower than yesterday, this means a
deeper cloud layer and better chance for drizzle through the
morning hours. The overall trend today will feature lifting
ceilings and/or clearing mid-day, moderate onshore winds in the
afternoon, and a return of MVFR-IFR stratus this evening.

Vicinity of SFO...MVFR ceilings at SFO and IFR ceilings at OAK
will persist through the early morning. There is a decent chance
that the ceilings never break at SFO and OAK. The skillful
GFSLAMP actually leans that way, but the current satellite shows
some holes in the stratus, and the persistence forecast suggests
at least a few hours of clearing in the afternoon. As such the
TAFs lean optimistic. The confidence is low, especially for OAK.

SFO Bridge Approach...The current satellite image shows some
clearing over the Bay, though it will likely close before the
heavier traffic arrives this morning.

Monterey Bay Terminals...MVFR-IFR ceilings with periods of drizzle
through the morning at MRY and SNS. Some improvement is expected
this afternoon with clearing at SNS and lifting ceilings at MRY.
The trickiest part is figuring out if MRY will clear at all
today. With boundary layer winds funneling moist air over the
Monterey Bay and only a thin layer of dry air above the marine
layer, the chances are good that ceilings will linger over parts
of the Monterey Peninsula all day. It`s still not clear whether
these clouds will remain over the terminal this afternoon or stay
confined to the immediate coastline.

&&

.MARINE...
(Today through Thursday)
Issued at 440 AM PDT Sat Jul 26 2025

Moderate northwest breezes and moderate seas prevail through
Tuesday with stronger gusts in the afternoons. Low clouds with
drizzle are expected this morning.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM to 9 PM PDT Sunday for Mry Bay-
     Pigeon Pt to Pt Pinos 0-10 nm-Pt Arena to Pt Reyes 0-10 nm.

     Small Craft Advisory from 3 PM Sunday to 3 AM PDT Monday for Pt
     Pinos to Pt Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...Flynn
MARINE...Flynn

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, X, and YouTube at:
www.facebook.com/nwsbayarea
x.com/nwsbayarea
www.youtube.com/nwsbayarea