442
FXUS66 KMTR 230108
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
601 PM PDT Fri Aug 22 2025

...New AVIATION, MARINE...

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

 - Heat Advisory continues today and tomorrow for inland areas,
   excluding the Santa Cruz Mtns, which expires tonight.

 - 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 1259 PM PDT Fri Aug 22 2025
(This evening through Saturday)

Current visible satellite showing some elevated CU and cirrus out
over the waters moving northward associated with a surge of
monsoonal moisture from our south. Aside from the Heat Advisories,
this will be the thing to watch for the next 18 hours. Hi-res CAMs
are rather finicky with this type of setup, but some do show some
elevated echos along the moisture axis which would drift over
Sonoma county late tonight into Saturday morning. This is very
much a low probability, high impact scenario, where the chance of
dry lightning is very low, but not zero. As mentioned in the
previous discussion, we do see the raw ingredients necessary for
dry lightning to occur. However, some aren`t quite the right
flavor. For example, much of this monsoonal moisture is confined
to levels higher up in the atmosphere than we`d like to see with
traditional and more impactful dry lightning setups. It`s really
one of those tricky setups where we most likely will not see any
lightning, but we wouldn`t be totally surprised if we saw a strike
or two. The good news here is that we aren`t expecting any strong
offshore winds over the forecast period. More in the FIRE WEATHER
section below.

In terms of warm temperatures today, the previous forecast was
running a few degrees warm as of this issuance, so decreased high
temps today a couple of degrees based on that and new guidance.
Therefore, we are not planning on extending any of the Heat
Advisories beyond their current expiration times (tonight for the
Santa Cruz Mtns, tomorrow night across the rest of the interior).

&&

.LONG TERM...
Issued at 1259 PM PDT Fri Aug 22 2025
(Saturday night through next Thursday)

Post Heat Advisories, temps look to drop back to around seasonal
normals by the start of next week as the ridge breaks down and a
weak, relatively stagnant upper low begins to form off the West
Coast. Still a week out, but ensemble guidance is beginning to
show some subtle hints at another surge of elevated moisture by
next weekend.

&&

.AVIATION...
(00Z TAFS)
Issued at 601 PM PDT Fri Aug 22 2025

Coastal stratus and fog /MVFR-IFR-LIFR/ have returned, the marine
layer depth is currently ~ 1500 feet. So far the coastal stratus
and fog within the marine layer appear independent from the monsoon
moisture i.e. there`s no disruption seen on visible satellite
imagery on the western periphery of the desert high pressure system.
Onshore winds will usher stratus and fog /IFR-LIFR/ inland tonight
and Saturday morning. Stratus and fog mixing out late Saturday morning
and afternoon, with a return of stratus and fog Saturday night and
Sunday morning.

Vicinity of SFO...Moderate to high confidence VFR continues through
the evening, IFR stratus ceiling is forecast 10z Saturday. Stratus
mixes out to VFR by late Saturday morning. Northwest wind gusts to
30 knots through 05z possibly decreasing somewhat overnight with west
to northwest wind near 25 knots resuming Saturday.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Stratus and fog /MVFR-IFR/ moving inland
tonight and Saturday morning. Clearing to VFR by late Saturday
morning, stratus and fog return Saturday night and Sunday morning.
Onshore winds 5 to 15 knots.

&&

.MARINE...
(Tonight through next Thursday)
Issued at 505 PM PDT Fri Aug 22 2025

Winds gradually diminish tonight into Saturday with fresh to
strong northwesterly gusts becoming moderate to fresh. Seas  will
continue to subside with calmer winds and seas expected this
weekend into the next work week. Locally stronger gusts are
anticipated in the favored coastal jet region near Point Sur on
Saturday with weaker coastal jets likely to develop over the
weekend.

&&

.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 PM PDT this evening for Pigeon Pt
     to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena
     to Pt Reyes 10-60 NM.

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

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

&&

$$

SHORT TERM...Behringer
LONG TERM....Behringer
AVIATION...Canepa
MARINE...RGass

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