FXUS66 KMTR 231854
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
1154 AM PDT Sun Aug 23 2026
...New AVIATION...
.KEY MESSAGES...
Updated at 1204 AM PDT Sun Aug 23 2026
- Temperatures near to slightly below seasonal averages persist
within the marine layer through the next week
- Warm and dry conditions continue above 1000 feet
&&
.UPDATE...
Issued at 920 AM PDT Sun Aug 23 2026
The marine layer remains much more compressed today with stratus
confined to coastal areas and patches of it along the SF Bay
shoreline. Stratus is expected to recede earlier today than
yesterday with high level clouds to persist through the day.
Otherwise, expect highs in the 80s across the interior with the
warmest interior locations reaching the 90s. Coastal areas will
stay cooler in the 60s to 70s.
&&
.SHORT TERM...
Issued at 1204 AM PDT Sun Aug 23 2026
(Today and tonight)
Another day of the weather pattern dominated by the balance between
the ridge over the Desert Southwest and the troughing over the
Eastern Pacific. Today, a cutoff low moving across the Pacific
Northwest is allowing the ridging to have a little more impact over
central California, resulting in a compressed marine layer and a
slight uptick in temperatures across the interior. Some coastal
stratus development is still possible through the overnight hours,
and any stratus that does form will dissipate rather early in the
post-sunrise hours. High temperatures today range in the middle 80s
to the middle 90s across the interior, the upper 90s into the triple
digits in the warmest interior spots (especially southern Monterey
County), the 70s and lower 80s near the Bays, and the lower to
middle 60s along the Pacific coast. Breezy onshore winds are
expected in the afternoon and evening along the coast and through
favored gaps and passes.
Regarding conditions near the Timber Fire, the compressed marine
layer will lead to warm and dry conditions in the higher elevations
where the fire continues to actively burn. Light northeast winds in
the morning will shift to a southwest flow in the afternoon and
evening hours. Smoke transport will be inhibited by the marine layer
inversion into the morning, resulting in the potential for reduced
visibilities in the immediate area, while winds aloft will transport
smoke northeastward towards Salinas and Hollister. For air quality
information, refer to products issued by the Monterey Bay Air
Resources District.
&&
.LONG TERM...
Issued at 1204 AM PDT Sun Aug 23 2026
(Monday through Saturday)
The pattern remains relatively stable through the rest of the
forecast period. A developing low in the eastern Pacific will allow
more of the troughing influence to arrive on Monday, causing
temperatures to dip by around 3-6 degrees in the inland valleys
(around the lower 80s to the lower 90s), before temperatures rebound
on Tuesday and Wednesday due to the ridging reasserting itself, and
remain remarkably close to today's forecast through the end of the 7-
day outlook. The breezy afternoon and evening winds will continue to
develop for coastal areas and through favored gaps and passes.
Ensemble models and our colleagues at the National Hurricane Center
continue to suggest the possibility for a couple of tropical systems
to develop off the coast of Mexico through the next week. One such
system could very well develop today. It's too early to say what the
impacts of the system could be to the region, ranging from impacts
to the large-scale pattern to the potential for tropical moisture
flow towards our region.
&&
.AVIATION...
(18Z TAFS)
Issued at 1154 AM PDT Sun Aug 23 2026
Widespread VFR conditions prevail through much of the afternoon with
gentle to moderate onshore breezes. IFR stratus will linger at HAF
into the early afternoon as the mixing of dry air continues along
the coast. The marine layer is expected to remain compressed around
1000 to 1200 feet tonight which will limit its inland expansion.
High confidence for IFR to LIFR ceilings to develop at the coast
with potential reductions to visibility. Medium confidence on STS
developing IFR ceilings given the lack of weak offshore winds aloft.
Overall, the wind flow above the marine layer will remain onshore
through the TAF period. Despite this, medium confidence on whether
APC will develop a ceiling given the shallow marine layer.
Vicinity of SFO...VFR through the day with onshore winds settling in
this afternoon. Medium confidence on low-end MVFR ceilings
developing at the terminals early Monday morning. Given the
prominent onshore flow and shallow marine layer, a later stratus
arrival is anticipated (09-12Z Monday). VFR conditions should
prevail by late Monday morning.
SFO Bridge Approach...Cloud cover overnight may be patchy over the
San Mateo bridge as stratus coverage is not expected to travel far
south into the Santa Clara valley. Otherwise, similar to SFO.
Monterey Bay Terminals...Northwest winds prevail at SNS through the
TAF period meanwhile MRY remains more west to southwest. Gentle to
moderate winds increase through the afternoon before easing and
becoming variable overnight. Medium confidence for an earlier onset
of stratus this evening around sunset with IFR-LIFR ceilings.
Reductions to visibility due to mist are possible overnight with the
compressed marine layer.
&&
.MARINE...
(Today through Friday)
Issued at 920 AM PDT Sun Aug 23 2026
Northwest winds remain moderate through Sunday and gradually ease
to gentle breezes through the middle of next week before
increasing again. The northern outer waters will continue to
experience near gale force gusts into the evening. Wind driven
seas remain slight to moderate entering the work week. Reduced
visibility due to smoke from the Timber Fire is expected along
the Big Sur coast as the marine inversion holds through the
morning.
&&
.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...DialH
LONG TERM....DialH
AVIATION...Navarrete
MARINE...Navarrete
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Prepared by Boulder-Creek.com Weather at: Sun Aug 23 12:30:02 PDT 2026
From the National Weather Service
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