FXUS66 KMTR 232339
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
439 PM PDT Sun Aug 23 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1237 PM PDT Sun Aug 23 2026

 - Near to slightly below normal temperatures persist in the
   marine layer this week

 - Warm and dry conditions continue above 1000 feet

&&

.SHORT TERM...
Issued at 1237 PM PDT Sun Aug 23 2026
(This evening through Monday night)

Not too much change in the forecast today as the Bay Area and 
Central Coast remain in between an upper level trough to the north 
and a ridge over the Desert Southwest. Ridging remains more dominant 
through this evening before the center of the ridge shifts eastward 
early Monday and troughing becomes more dominant over the region. 
High temperatures are forecast to peak in the upper 80s to low 90s 
across the interior with far interior Monterey County reaching the 
low 100s. Coastal areas are benefiting from a shallow (~1000 foot) 
marine layer that brought patchy stratus and drizzle to the coast 
and the SF Bay shoreline. This will keep temperatures cooler in 
coastal areas with highs peaking in the 60s to low 70s. 

Heading into Monday, the center of the upper level ridge will shift 
eastward with troughing becoming the dominant feature over us. The 
return of troughing will help the marine layer to (slightly) deepen 
and bring it from approximately 1000 ft to 1200-1500 ft. A slightly 
deeper marine layer will allow for a greater inland intrusion of 
stratus, but, stratus is not likely to be as widespread as it was 
last week. Temperatures are expected to drop by around 5 degrees for 
most interior locations. This will see a return of highs in the low 
to mid 80s while the higher elevations above the marine layer will 
stay comparatively warmer in the upper 80s to low 90s. Coastal areas 
will remain in the 60s to low 70s with additional periods of coastal 
drizzle likely during the early morning hours. The one questionable 
part of the forecast is if any thunderstorms will be able to develop 
across the North Bay Interior Mountains (particularly Napa County) 
early Monday morning. The Euro suggests that there will be 
sufficient moisture, instability, and lift as a weak shortwave 
trough moves in to California for orographically driven 
thunderstorms to develop there early Monday morning. NBM guidance 
gives around a 5% chance of thunderstorms developing. Any 
precipitation that falls would likely be virga/evaporate before 
reaching the surface given model Skew-T soundings showing a large 
dry layer between the mid and lower levels of the atmosphere. 
Confidence remains low overall in storm development, however, as 
other models (GFS, NAM, HRRR, RRFS) do not support storms developing 
tomorrow morning with the Euro being an outlier.

&&

.LONG TERM...
Issued at 1237 PM PDT Sun Aug 23 2026
(Tuesday through next Saturday)

Troughing prevails through Tuesday with high temperatures remaining 
in the 60s to 70s along the coast, 80s across the interior, upper 
80s to low 90s across the higher elevations, and upper 90s to low 
100s across the interior Central Coast. Stratus is expected along 
the coast and portions of the SF Bay shoreline but continues to be 
limited in extent. The center of the upper level ridge shifts back 
westwards Wednesday to Thursday with high temperatures warming by 
around 5 degrees across the interior (largely returning temperatures 
to the upper 80s to 90s). Friday into the weekend, temperatures cool 
by a few degrees as ridging weakens and troughing 
deepens/strengthens over the Pacific. Troughing looks to continue 
into next week with a deep upper level low moving into the Pacific 
Northwest and Northern California. It will be worth keeping an eye 
on this incoming trough and the arrival of any potential tropical 
moisture towards the end of the forecast period. The latest NHC 
guidance shows three active areas of tropical interest offshore of 
Mexico with recently named TS Iselle in the vicnity as well. 
Guidance is starting to indicate some tropical moisture from these 
systems may be brought north as the trough arrives but it is unclear 
how far north this tropical moisture will go. Some models keep it 
more over Southern California while others bring it up into 
Monterey/San Benito counties. Models are already showing an increase 
in southerly swell associated with the uptick in tropical activity 
across the Eastern Pacific this weekend into early next week.

&&

.AVIATION...
(00Z TAFS)
Issued at 439 PM PDT Sun Aug 23 2026

VFR continues except for patchy coastal stratus and fog /MVFR-
IFR/. Mid and high clouds, including wildfire smoke over the north
Central Coast, are moving northeastward over the forecast area. 
Coastal stratus and fog /MVFR-IFR-LIFR/ redevelop tonight and 
Monday morning. Conditions improve to MVFR-VFR along the coast
late Monday morning and afternoon otherwise VFR Monday.

Vicinity of SFO...VFR prevails until stratus /MVFR/ develops 12z 
Monday. VFR returns 18z Monday. West wind 5 to 15 knots with 
occasional afternoon and evening gusts near 20 knots.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR then stratus /IFR-LIFR/ moves inland 
mid to late evening to Monday morning. Conditions improve to MVFR-
VFR late Monday morning and afternoon. West to northwest winds 5 
to 15 knots.


&&

.MARINE...
(Tonight through next Friday)
Issued at 433 PM PDT Sun Aug 23 2026

Moderate northwest breezes gradually diminish this evening and
become gentle by tomorrow. Occasional strong gusts are possible
this  Sunday afternoon, particularly across the Northern outer
waters and  near the Big Sur coast. Slight to moderate wind driven
seas prevail  into the work week.

&&

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

&&

$$

SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...Canepa
MARINE...Navarrete

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Prepared by Boulder-Creek.com Weather at: Sun Aug 23 20:30:03 PDT 2026