FXUS66 KMTR 250703
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
1203 AM PDT Tue Aug 25 2026
...New SHORT TERM, LONG TERM, FIRE WEATHER...
.KEY MESSAGES...
Updated at 1202 AM PDT Tue Aug 25 2026
- Temperatures near to slightly below seasonal averages persist
within the marine layer through Thursday
- Seasonably warm and dry conditions continue above 1000 feet
- Pattern change Friday into the weekend brings cooler
temperatures and moderate potential for tropical moisture
&&
.SHORT TERM...
Issued at 1202 AM PDT Tue Aug 25 2026
(Today and tonight)
Satellite imagery shows an expanding stratus layer below
scattered high clouds, with low clouds present in the valleys of
southern Sonoma County, the San Francisco Bay region, and down the
Salinas Valley. Coastal drizzle has been observed at the office,
and has been added to the grids tonight. The stratus deck is
expected to continue developing into the SF Bay region through the
night before retreating back to the coastal regions after
sunrise.
After a slight dip in the temperatures yesterday, temperatures will
tick upward today as the balance between troughing in the eastern
Pacific and ridging over the Desert Southwest swings back towards
the ridging influence. Temperatures range from the 80s into the
middle 90s for the inland valleys, up to around 104 in the southern
tier of Monterey County, the upper 60s to the lower 80s near the
Bays, and the upper 50s to middle 60s along the Pacific Coast.
Breezy onshore winds will develop this afternoon and evening, with
wind gusts 20 to 30 mph along the coast and through favored gaps and
passes. The marine layer will remain around 1000-1500 ft today, with
warm and dry conditions above the marine layer inversion. See the
FIRE WEATHER section for the implications for local fire weather
concerns.
&&
.LONG TERM...
Issued at 1202 AM PDT Tue Aug 25 2026
(Wednesday through Monday)
The ridging prevails into Thursday with temperatures in the middle
80s to the middle 90s inland and the 70s into the middle 80s near
the Bays. A pattern change begins on Friday with upper level
troughing developing over the West Coast, bringing cooler
temperatures and breezier winds to the region. Temperatures in the
inland valleys dip into the 80s for the weekend, and cool further
with highs dipping into the middle 70s to lower 80s early next week.
Even the warm spots of the interior Central Coast cool into the
middle to upper 80s by Monday. The strengthening pressure gradient
will allow stronger onshore flow to develop starting on Friday, with
wind gusts of 25 to 35 mph expected along the coast, through favored
gaps and passes, and within the northern Salinas Valley.
We continue to monitor an active tropical Eastern Pacific and its
indirect impacts to the region. Tropical Storm Iselle continues to
march northwestward off the coast of western Mexico, and a Tropical
Depression has spun up for around a day or so before it gets
absorbed into Iselle. In addition, our colleagues at the National
Hurricane Center are tracking three potential development areas
through the next week. None of these storms are expected to directly
impact the state, but long-period swell generated by the intense
winds within the storms is expected to begin arriving Friday into
the weekend. The current forecast remains just below Beach Hazards
Statement criteria, but this will get refined through the next
couple of days. There's also an increasing chance that tropical
moisture will impact the region during Friday and the weekend, with
the model trend being to push the moisture plume farther up the
coast into the Bay Area and Central Coast. The NBM continues to show
a very low (below 5% probability), but non-zero, chance for
thunderstorms during this period, and given the uncertainties
surrounding eastern Pacific tropical weather, this setup bears
continued monitoring.
&&
.AVIATION...
(06Z TAFS)
Issued at 940 PM PDT Mon Aug 24 2026
The marine layer is roughly 1,000 feet deep and well organized.
As the marine layer makes its nightly push inland, IFR-LIFR
conditions will be widespread across nearly all of the terminals
through the night and most of the morning. The visibility is a
little more uncertain, but some patchy fog is likely. Low clouds
should start to clear for all but the coastal airports by late
morning.
Vicinity of SFO...IFR ceilings have arrived and there is a high
probability they will remain for at least the next 12 hours. There
is a 40% chance that the visibility drops below VFR criteria after
10Z.
SFO Bridge Approach...Similar to SFO, although the ceilings
haven't formed yet and they will clear earlier than the terminal
Tuesday morning.
Monterey Bay Terminals...LIFR ceilings are essentially guaranteed
through the night and most of the morning. While SNS will likely
clear in the late morning, MRY may only see ceilings lift to IFR
in the afternoon before dropping back down to LIFR Tuesday
evening. If it does clear, it probably won't be for more than 6
hours.
&&
.MARINE...
(Tonight through next Sunday)
Issued at 917 PM PDT Mon Aug 24 2026
The increasing gradient between high pressure over the Eastern
Pacific and lower pressure over California will cause winds to
increase to a fresh NW breeze through the day tomorrow and winds
will remain fresh to strong through the week. A long period
southerly swell around 15 to 17 seconds approaches our coastal
waters by the end of the week.
&&
.FIRE WEATHER...
Issued at 1202 AM PDT Tue Aug 25 2026
Near-critical fire weather conditions continue through Thursday for
elevations above 1000 feet as warm and dry conditions continue
across the region. Humidity recoveries remain poor to very poor in
the higher elevations, with nocturnal drying expected within the
Santa Lucia range. Breezy conditions will develop each afternoon and
evening, but not for a long enough period to trigger any fire
weather products. Specifically regarding the Timber Fire vicinity,
observational data suggests that southwesterly winds from the
Pacific Ocean over the ridgetops are helping to moisten the air,
with nocturnal drying being observed as the winds diminish and even
turn faintly offshore overnight. This has led to an unusual
situation where daily maximum relative humidity values have been
observed during the daytime. Smoke transport from the Timber Fire
will continue to peak in the afternoon and evening with the plume
spreading towards the Salinas area. Friday into the weekend, a
pattern change should allow for some relief as an upper level trough
comes into the region bringing cooler temperatures and a deeper
marine layer.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 9 AM PDT
Wednesday for Pt Arena to Pt Reyes 0-10 nm-Pt Pinos to Pt
Piedras Blancas 0-10 nm.
Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this
evening for Pigeon Pt to Pt Pinos 0-10 nm.
Small Craft Advisory from 9 PM this evening to 9 AM PDT
Wednesday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt
Reyes 10-60 NM.
&&
$$
SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Flynn
MARINE...Flynn
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Prepared by Boulder-Creek.com Weather at: Tue Aug 25 00:30:03 PDT 2026
From the National Weather Service
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