FXUS66 KMTR 251156
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
456 AM PDT Tue Aug 25 2026

...New AVIATION, MARINE...

.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...
(12Z TAFS)
Issued at 431 AM PDT Tue Aug 25 2026

A robust marine layer was measured at ~1800ft with the KOAK 12z
balloon with primarily IFR/LIFR conditions with the exception of
KAPC, KSJC and KLVK. Mid/high level cloud cover likely helping to
keep the latter three terminals in MVFR/VFR through mid-morning.
Majority of terminals are expected to lift to VFR by late morning,
with KMRY having a 30% chance of lingering past Noon PDT.

Vicinity of SFO...Should remain IFR through mid/late morning
before lifting to VFR for the remainder of the day and evening
hours. KOAK may see MVFR/IFR ceilings return soon after sunset
with KSFO more likely around midnight.

SFO Bridge Approach...Similar to KOAK with timing of ceilings.

Monterey Bay Terminals...Marine layer is not as deep this far
south, however LIFR ceilings are expected to persist through late
morning, clearing out of KSNS first with KMRY possibly lingering
into early afternoon with VFR until late afternoon early evening.
IFR/LIFR conditions expected from that point on for the remainder
of the forecast period.

&&

.MARINE...
(Today through Sunday)
Issued at 431 AM PDT Tue Aug 25 2026

Fresh breezes today will become fresh to strong on Wednesday and
persist through the remainder of the week into the weekend with
moderate seas. Long period southerly swell will begin to build on
Thursday, becoming 15 to 17 seconds for Friday and Saturday, then
begin to gradually ease on Sunday into next 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 
     Thursday for Pigeon Pt to Pt Pinos 0-10 nm-Pt Arena to Pt 
     Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory from 9 PM this evening to 9 AM PDT Thursday 
     for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-
     60 NM.

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...JM
MARINE...JM

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, X, and YouTube at:
www.facebook.com/nwsbayarea
x.com/nwsbayarea
www.youtube.com/nwsbayarea


  
Prepared by Boulder-Creek.com Weather at: Tue Aug 25 06:30:03 PDT 2026