884
FXUS66 KMTR 221054
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
354 AM PDT Fri Aug 22 2025

...New SHORT TERM, LONG TERM, FIRE WEATHER...

.KEY MESSAGES...
Updated at 1206 PM PDT Thu Aug 21 2025

 - A Heat Advisory is in effect for much of the Bay Area and
   Central Coast today for areas away from the ocean.

 - Heat advisories continue for many inland areas through
   Saturday.

 - Stay hydrated and avoid strenuous activities during the
   hottest part of the day.

&&

.SHORT TERM...
Issued at 237 AM PDT Fri Aug 22 2025
(Today and tonight)

Current situation: Interesting setup on satellite imagery
overnight showing a marine layer redeveloping along the coast and
locally inland as upper level clouds/moisture stream from the
south and a notable heat signature from the Pickett Fire in Napa
county. More on Pickett Fire in the fire section below. The marine
layer is showing up at roughly 800 ft per profilers and is a
little more pronounced than 24 hours ago. Given the shallow nature
of the marine layer patchy fog will be possible along the coast
with pockets of fog down to a mile or less. It`s also another mild
night above the marine layer with temperatures well into the 70s
above 1500 feet with several low 80s above 2000 feet.

Today and tonight: No major changes to ongoing Heat Advisories
across the Bay Area and Central Coast. It will be another hot one
away from any marine influence with temps in the 90s to lower
100s and HeatRisk in the Moderate to Major (pockets of Extreme).
It`s Friday and you may have afternoon/evening outdoor plans so be
mindful of the heat and take appropriate action. Given the
ongoing fire in Napa county smoke has been added to the forecast
for portions of the North Bay. For tonight - more relief will be
felt over the lower elevations as the marine layer will deepen to
about 1k feet. Expect more stratus coverage by Saturday morning.
Above the marine layer will be mild and dry once again.

The fly in the ointment so to speak is the ongoing non-zero threat
for showers and dry lightning late today and Saturday. 00Z model
suite continues to paint a similar picture from the last few runs.
One cannot deny the monsoonal moisture advection from the south
given latest satellite imagery. Additionally, guidance has been
rather persistent on some upper level instability (MUCAPE/lapse
rates/HLTT). Some of the "hotter" CAMs paint a decent amount of
showers on modeled reflectivity imagery as well. Dry lightning
and high based convection scenarios are rather finicky and you
need all of the ingredients to line up just right. In this case,
they aren`t and that`s why this portion of the forecast remains
low confidence. While we do have some moisture/instability it`s
about where they overlap or don`t. x-sections and pt soundings
continue to show the moisture is rather high up and not
necessarily overlapping with best instability. Moisture remains
in the 500-550mb level. Would like to see moisture lower and at
least closer to 600mb. Previous historic dry lightning events show
moisture much higher in the 600-700mb. Therefore, will continue
to mention the low chc in the AFD and not in the official
forecast.


&&

.LONG TERM...
Issued at 340 AM PDT Fri Aug 22 2025
(Saturday through Thursday)

One final day of real impactful heat with Heat Advisories
remaining for the interior with highs in the 90s to lower 100s.
Much more relief is expected along the coast and locally inland.
The non-zero threat for showers/dry lightning remain for Saturday
as well. Highest likelihood would be for eastern portions of the
forecast area bordering the Central Valley.

The ridge that brought record breaking heat will begin to fade by
Sunday. An upstream upper trough begins to move in by Monday as
the ridge exits eastward. As such a gradual cooldown is expected
through the middle of next week.

&&

.AVIATION...
(06Z TAFS)
Issued at 934 PM PDT Thu Aug 21 2025

Widespread VFR lasts into the late night. Expect winds to reduce
into the night, becoming light for most areas. Stratus struggles to
form overnight; LIFR CIGs look to build at HAF, with only spotty
LIFR CIG coverage expected around OAK and the Monterey Bay
terminals. Low clouds look to erode in the mid morning with
widespread VFR expected by Friday afternoon as moderate to breezy
winds return. LIFR CIGs return to HAF in the mid evening as winds
reduce. CIGs look to return to the bays later into that night as
winds become light.

Vicinity of SFO...VFR through the TAF period. Winds stay moderate
and westerly through the night and into Friday afternoon. Expect
winds to into the mid afternoon with gust peaking around 25 kts.
These winds and gusts last though the evening before gusts ease and
wind become more moderate into Friday night.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR lasts into the early morning. Winds
stay light through the night. Spotty LIFR CIGS and reductions in
visibilities look to affect the terminals early Friday morning but
exit in the mid morning. Expect moderate winds to build again for
Friday afternoon but become light again into the night with CIGs
arriving in the late night, shortly beyond the TAF period.

&&

.MARINE...
(Tonight through next Wednesday)
Issued at 934 PM PDT Thu Aug 21 2025

Moderate to breezy winds last through Friday, with locally
stronger gusts especially across the outer waters and coastal jet
regions near Point Sur and Point Reyes. This will result in
widespread hazardous conditions for small craft. Winds and seas
will gradually ease Friday afternoon and evening, leading to
calmer conditions over the weekend and well into the next work
week.

&&

.FIRE WEATHER...
Issued at 344 AM PDT Fri Aug 22 2025

Pickett Fire in N Napa county. Cams and satellite both indicate
active fire behavior overnight. This makes sense given nearby
weather stations showing temps in the 70s/low 80s and RH values in
the upper teens to 30% ranges. Simply put, mild and dry. Winds
thankfully aren`t overly strong. Occasional gusts to 10 mph are
being observed over the highest peaks.

Elevated fire weather concerns remain and not just because of the
new Pickett Fire. The combo of hot/dry conditions remain both day
and night for today and at a minimum Saturday. Expect another
onshore push of afternoon/evening winds, which will coincide with
peaking heating. We`ll finally see fire weather conditions
improve late in the weekend and early next with the cooldown.
Lastly, as mentioned above we continue to monitor the non-zero
chance for dry lightning and showers. Given the moisture profile
of the atmosphere developed storms/showers will likely be drier in
nature. That would lead to gusty outflows, which could be
problematic if they occur near the Pickett Fire.

MM

&&

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

     Heat Advisory until 10 PM PDT this evening for CAZ512.

PZ...Small Craft Advisory until 9 AM PDT this morning for Pt Arena to
     Pt Reyes 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

     Small Craft Advisory until 9 PM PDT this evening for Pigeon Pt
     to Pt Pinos 0-10 nm.

     Small Craft Advisory until 3 AM PDT Saturday for Pt Pinos to Pt
     Piedras Blancas 0-10 nm.

     Small Craft Advisory until 9 PM PDT this evening for Pigeon Pt
     to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...Murdock
MARINE...Murdock

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