546
FXUS66 KMTR 231724
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1024 AM PDT Sat Aug 23 2025

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1259 PM PDT Fri Aug 22 2025

 - Heat Advisory continues today for inland areas.

 - Stay hydrated and avoid strenuous activities during the hottest
   part of the day if you`re outside in the advisory areas.

 - Temperatures gradually cool through the weekend, back to
   seasonal normals by next week.

&&

.SHORT TERM...
Issued at 234 AM PDT Sat Aug 23 2025
(Today and tonight)

Overnight satellite looks a little different than 24 hours ago.
The marine layer is more developed tonight with widespread
coastal stratus pushing into the inland valleys. Profilers put the
depth around 1200 feet. Given the shallow nature could even see
some patchy fog and drizzle along the coast this morning. MRY and
HAF sensors both show vsby at or less than 3 miles. Additionally,
cams at HAF airport even show drizzle. Water vapor imagery
continues to show the much talked about moonsonal moisture riding
the western edge of the ridge tracking up the CA coast. The IR
channel indicates that some of this moisture is deeper with lift
resulting in cooling cloud tops west of Pt Conception. In fact,
KMUX and KVBX radars are picking this up too with possible
showers over the coastal waters. Given the current atmospheric
profile these returns are likely virga and not reaching the
ground. That being said, did include a 15% chc for showers over
the coastal waters this morning. What about precip chances for
the rest of the day? 00Z CAMs once again paint a picture of
moisture and lift, but struggle to have it overlap in a way to
produce convection over the forecast area. However, could see some
high based virga, which could lead to some gusty surface winds in
the vicinity. While the best overlap of moisture and instability
this afternoon will be over the Sierra there is some that will
brush eastern parts of the forecast area/bordering the CEntral
Valley. Will be watching, but for now the forecast remains dry.

Other notable item for today will be one final day of impactful
heat. Heat Advisories remain in effect through this evening for
interior locations. Basically, areas not being effect dramatically
by the marine layer. 850mb temperatures this afternoon are still
on track to reach about 25C, which would once again yield max
temps in the upper 90s to lower 100s. Smoke remains in the
forecast for the N Bay due to the Pickett Fire. For tonight,
expect night with a marine layer. The marine layer has a chance
to be a tad deep and closer to 1500 feet. Still could see some
drizzle/fog along the coast. Above the marine will still be
relatively mild and dry.

&&

.LONG TERM...
Issued at 311 AM PDT Sat Aug 23 2025
(Sunday through Friday)

The grip the ridge of high pressure had on the region begins to
ease as an upstream trough begins to approach. In other words, as
we end the weekend begin a new work week temperatures begin to
cool and transition back to seasonable levels. While temperatures
do begin to cool and no heat advisories are in effect for Sunday
we still see temps reach triple digits for far interior locations.
By midweek temperatures are back to seasonal averages with night
and morning clouds. For those playing the long range forecast game
at home a few global models bring a tropical system northward
late in the forecast period. As this happens another upper low
forms off the PacNW. Stay tuned...

&&

.AVIATION...
(18Z TAFS)
Issued at 1022 AM PDT Sat Aug 23 2025

VFR conditions returning to much of the region this morning, the
exception is HAF where LIFR/IFR are likely to persist through much
of the TAF period. Onshore winds are again forecast to increase this
afternoon and then ease after sunset and into early Sunday morning.
Moderate to high confidence for IFR/MVFR ceilings to return to the
Bay Area terminals late this evening and persist through about 17Z-
19Z on Sunday. High confidence of an early return this evening for
LIFR/IFR conditions at the Monterey Bay terminals that will likely
persist through the TAF period.

Vicinity of SFO...VFR. West to northwest winds are forecast to
increase again this afternoon with gusts up to 25 kt at SFO. Winds
ease after sunset yet remain out of the west/northwest through much
of the night with moderate to high confidence for IFR/MVFR ceilings
to return to the terminals late this evening and persist through
about 17Z-19Z on Sunday. Once low clouds clear, onshore winds will
increase once again Sunday afternoon.

SFO Bridge Approach...Moderate to high confidence for IFR/MVFR
ceilings are expected Sunday morning from about 06Z-17Z. Low
ceilings are likely to clear out by 17Z. Otherwise, similar to SFO.

Monterey Bay Terminals...VFR. Onshore winds increase this afternoon
before easing after sunset. High confidence of an early return this
evening for LIFR/IFR conditions at the terminals that will likely
persist through the TAF period.

&&

.MARINE...
(Today through Thursday)
Issued at 1022 AM PDT Sat Aug 23 2025

Winds have diminished across the coastal waters with a moderate to
fresh northwesterly breeze to persist into next week. Locally
stronger gusts are anticipated in the favored coastal jet region
near Point Sur on Saturday. Winds increase and seas build briefly
during the early work week across the northern outer waters before
both diminish by midweek.

&&

.FIRE WEATHER...
Issued at 315 AM PDT Sat Aug 23 2025

For the Pickett Fire: Another active night on the fire as heat
signature remain on satellite. Cams in the N Napa also show active
fire behavior. So why the active behavior? Topography and thermal
belts. Most active fire appears to be above 1500 feet. Weather
stations above 1500-2000 feet still show temperatures in the 70s
to lower 80s at 3 AM with moderate to poor humidity. Thankfully,
winds are relatively light and mostly terrain driven. While the
marine layer has returned and brought some better humidity to the
Napa Valley the fire still remains above it. Expect and another
hot and dry day. Light winds in the morning with a more westerly
influence this afternoon with gusts in the 15 mph range.

Elsewhere: No change from previous discussion. Hot and dry
conditions persist through at least Saturday due to high pressure
over the region, creating elevated fire weather conditions across
the interior, as exemplified by a couple of fire starts through
Friday. Breezy onshore winds develop each afternoon and evening
with gusts reaching 20 to 25 mph through favored gaps, passes,
valleys, and coastlines. Monsoonal moisture coming through the
area continues to bring a very low, but non-zero, chance of dry
thunderstorms to the region through Saturday. As the ridge breaks
down on Sunday, cooler and moister conditions should arrive,
although the interior Central Coast may hang on to the hot and dry
conditions until Monday. One fire highlight through midweek could
be a situation where nocturnal drying events return, especially
the higher peaks of the Central Coast.

MM

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 9 PM PDT this evening for CAZ504-510-513>518.

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

&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...RGass
MARINE...RGass

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