FXUS66 KMTR 270703
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
1203 AM PDT Thu Aug 27 2026
...New SHORT TERM, LONG TERM, BEACHES...
.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...
(06Z TAFS)
Issued at 841 PM PDT Wed Aug 26 2026
It's VFR across the forecast area except in the area of the Timber
Fire smoke and haze may reduce slant range and surface visibilities.
24 hour trends continue mainly warmer and drier across the forecast
area and satellite imagery shows stratus and fog recently reaching
the coastline. The ACV-SFO pressure gradient is 4.0 mb and the
SFO-SAC pressure gradient is 2.5 mb. Coastal stratus and fog
/IFR-LIFR/ will redevelop tonight and Thursday morning under a
compressed marine layer. Coastal stratus and fog mix out to VFR by
late Thursday morning and afternoon.
Vicinity of SFO...VFR. West wind easing to near 10 knots tonight and
Thursday morning. West wind increasing to 20 to 25 knots Thursday
afternoon to mid evening.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR except tempo stratus and fog /IFR-LIFR/
11z-15z Thursday morning. Mid level clouds may result in a passing
high based shower Thursday afternoon.
&&
.MARINE...
(Tonight through next Tuesday)
Issued at 837 PM PDT Wed Aug 26 2026
Fresh to strong northwest winds will continue tonight and into
the weekend with moderate wind driven seas. Occasional gale force
gusts in the outer and inner waters are expected through the
weekend. A long period southerly swell will build late in the week
becoming 17-18 seconds by Friday and persist through at least
early Sunday.
&&
.BEACHES...
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 Friday 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...Canepa
MARINE...Canepa
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Prepared by Boulder-Creek.com Weather at: Thu Aug 27 00:30:02 PDT 2026
From the National Weather Service
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