FXUS66 KMTR 271150
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
450 AM PDT Thu Aug 27 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1201 AM PDT Thu Aug 27 2026

 - Slight chance of thunderstorms this morning, with shower
   chances through Friday

 - Slight cooling today, with temperatures close to seasonal averages

 - Cooling trend continues Friday into the next week

&&

.SHORT TERM...
Issued at 1201 AM PDT Thu Aug 27 2026
(Today and tonight)

Stratus clouds are developing at the immediate coast and are 
expected to generally remain confined to the coastal valleys 
overnight before mixing out through Thursday morning. Zooming out 
into the Pacific reveals some interesting activity off the coast as 
some storm cells with frequent lightning have developed around a 
moisture gradient. The latest forecast update includes a slight 
chance for thunderstorms for the morning hours, around the time 
that these cells would impact the coast if they hold together. As 
of the time of writing, they have been dissipating as they move 
towards our coastal waters, but the night shift will continue 
monitoring these cells as they approach and issue any forecast 
updates and products as they become necessary. Beyond the morning 
hours, tropical moisture sourced from the remnants of Tropical 
Storm Iselle will come into the state, and slight chances for 
showers persist through the day. Low, but non-zero, chances for 
thunderstorms will tick up again in the afternoon and evening 
hours, but the limiting factor appears to be insufficient 
atmospheric instability. Will continue to monitor the situation as
it evolves through the day.

The large-scale weather pattern remains dominated by the balance 
between the ridging over the Desert Southwest and the troughing over 
the eastern Pacific. The ridging has generally won out over the last 
few days, but today will mark the very beginnings of a transition to 
a more troughing-dominated pattern. Temperatures will remain near to 
slightly above the seasonal averages, but we will see a slight 
cooldown as highs reach the upper 80s to middle 90s inland, the 
upper 90s to the triple digits in the warmest interior locations, 
the lower 70s to the lower 80s near the Bays, and the lower to 
middle 60s at the Pacific coast. Breezy onshore winds will develop 
in the afternoon and evening hours with gusts of 20 to 30 mph at the 
coasts.

For a discussion of weather-related impacts to the fire weather 
situation, see the FIRE WEATHER section.

&&

.LONG TERM...
Issued at 1201 AM PDT Thu Aug 27 2026
(Friday through Wednesday)

The progression of the trough, and with it the cooling trend and 
associated tropical moisture, continue into Friday with the slight 
chances for showers continuing through the day. Later on Friday into 
the weekend, the tropical moisture dips to the south but the 
deepening trough remains, and cooler temperatures continue into the 
middle of next week. Temperatures reach their coolest on Monday, 
around 5 to 15 degrees below seasonal averages, as high reach the 
70s throughout the inland valleys, the 80s along the warmest 
interior Central Coast regions, and the upper 50s to the 60s at the 
Bays and the Pacific coast. The trough will start to flatten out, 
but remains in place with temperatures slow to rise. The forecast 
shows rain chances returning to the region for the middle of next 
week, but this is critically dependent on how conditions evolve in 
the tropical Eastern Pacific, so confidence remains low.

&&

.AVIATION...
(12Z TAFS)
Issued at 428 AM PDT Thu Aug 27 2026

VFR prevails with the exception of KHAF. The marine layer has
remained around 1000ft, unorganized and made little to no inland 
push through the overnight hours. VFR is expected to prevail for
most terminals through the forecast period. Confidence is low on
the potential for IFR/LIFR ceilings developing late in the
forecast period along the coastal sites, especially KMRY and KSNS.

Vicinity of SFO...The marine layer has remained at the coastline
overnight. A fetch of offshore flow just above the marine layer
will help maintain VFR conditions now through late tonight into 
early Friday morning. Will have to see how well the marine layer 
recovers once flow in the lower boundary layer returns to onshore 
late in the forecast period.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR with a slight chance of LIFR ceilings
until mid-morning. Offshore flow this far south is more pronounced
and expected to help maintain VFR conditions through the forecast
period. There is a slight chance of showers developing offshore
and moving through the Central Coast and Monterey Bay terminals
through the forecast period. Elevated thunderstorms are not
currently in the forecast, and chances remain low, but cannot be
ruled out entirely.

&&

.MARINE...
(Today through Tuesday)
Issued at 428 AM PDT Thu Aug 27 2026

Fresh to strong northwest winds will persist today and continue
into the weekend with moderate wind driven seas. Near gale force
gusts are possible over the northern outer and coastal waters
this afternoon into tonight. A long period southerly swell will
begin to build above 16 seconds Friday morning, peaking around
17-18 seconds by Saturday morning, and gradually decline Sunday
into Monday.

&&

.FIRE WEATHER... 
Issued at 1201 AM PDT Thu Aug 27 2026

One more day of near-critical fire weather conditions above 1000 
feet, especially across the Central Coast, as warm and dry 
conditions continue above the marine layer inversion and overnight
humidity recoveries remain poor. One thing to note is that even 
with the slight chance of rain today into Friday, we are not 
expecting wetting rains to develop, while a small but non- zero 
chance for thunderstorms raises the specter for a dry lightning- 
induced fire start in the higher elevations. Across the Timber and
Plaskett Fires, light offshore winds overnight may lead to 
nocturnal drying concerns at the higher elevations. A pattern 
change Friday into the weekend will bring cooler temperatures and 
likely a deeper marine layer, bringing progressively more relief 
to some of the higher elevations. 

DialH

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 AM PDT Saturday for Pigeon Pt to Pt 
     Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt 
     Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM-Pt Pinos to Pt 
     Piedras Blancas 0-10 nm.

&&

$$

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

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Prepared by Boulder-Creek.com Weather at: Thu Aug 27 06:30:03 PDT 2026