Technical NOAA Weather Discussion

FXUS66 KMTR 210520
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1020 PM PDT Thu Aug 20 2026

...New SHORT TERM, LONG TERM...

.KEY MESSAGES...
Updated at 1017 PM PDT Thu Aug 20 2026

 - Temperatures will be close to or below normal into the
   beginning of next week

 - Warm and dry conditions above 1000ft persist into the weekend

&&

.SHORT TERM...
Issued at 1017 PM PDT Thu Aug 20 2026
(Friday and Friday night)

Improved onshore flow in the lower boundary layer especially for the 
North Bay and Bay Area should result in more extensive stratus 
intrusion overnight coinciding with overnight lows closer to normal 
for this time of year. Warm and dry conditions will continue both 
overnight and through the day above 1000ft inland and near the 
coast, this includes in vicinity of the Timber Fire where relatively 
light winds continue to be a mitigating factor. Some elevated 
convection earlier Thursday night has tapered off or now in the 
steering flow of the ridge. Any mid/upper level moisture attempting 
to reach the Central Coast would be greeted by anemic instability 
and confluent flow aloft.

As the closed portion of the upper level low responsible for the 
persistent troughing recently will slowly approach the Oregon coast 
later tonight with a steady fetch of onshore flow continuing across 
our area, with only a marginal increase in depth of the marine layer 
expected into early Saturday morning.

&&

.LONG TERM...
Issued at 1017 PM PDT Thu Aug 20 2026
(Saturday through next Thursday)

The parent low mentioned above moves onshore into the PacNwest 
during the day Saturday with a weak troughing pattern lingering 
offshore at our latitude through at least the weekend. However, the 
persistent ridging over the Desert Southwest will shift east as well 
during this time , thus we'll continue to see the cooling trend 
through the weekend into the beginning of next week. There's a weak 
signal for the ridging to the east to build back toward the west 
coast by the middle of next week, which would bring warmer 
temperatures, but at that point a potential tropical system well to 
our southwest may add noise to the NWP.

&&

.AVIATION...
(06Z TAFS)
Issued at 849 PM PDT Thu Aug 20 2026

It's VFR except onshore winds will usher stratus and fog /MVFR-IFR-
LIFR/ inland tonight and Friday morning. Patchy coastal drizzle is
possible tonight and Friday morning. Conditions improve to MVFR-VFR
late morning and afternoon Friday.

Vicinity of SFO...Stratus /MVFR-IFR/ continues tonight and Friday
morning, with mix out to VFR forecast 19z Friday. Stratus /MVFR/
returns Friday night and Saturday morning. West-northwest wind 15
to 25 knots until 08z tonight then easing to 12 to 15 knots tonight
and Friday morning then increasing to 15 to 25 knots Friday afternoon
and evening. 

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Stratus, fog /MVFR-IFR-LIFR/ and possibly
a few patches of drizzle developing tonight and Friday morning.
Conditions improving to MVFR-VFR Friday afternoon. Stratus /MVFR-IFR/
returns Friday evening and night. West to northwest winds 5 to 15
knots.

&&

.MARINE...
(Tonight through next Wednesday)
Issued at 841 PM PDT Thu Aug 20 2026

Northwest moderate to fresh breezes persists into the weekend with
higher winds expected near the coastal jet regions of Point Reyes
and Point Sur. Occasional strong gusts are possible across the
outer  waters and coastal jet areas through Saturday. Wind driven
seas  remain slight at the coastline and quickly build to moderate
across  the outer waters through the weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Friday for Pt Arena to Pt 
     Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.

     Small Craft Advisory from 11 AM to 9 PM PDT Friday 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.

&&

$$

SHORT TERM...JM
LONG TERM....JM
AVIATION...Canepa
MARINE...Canepa

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Prepared by Boulder-Creek.com Weather at: Fri Aug 21 00:30:03 PDT 2026
From the National Weather Service