934
FXUS66 KMTR 081800
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1100 AM PDT Wed Oct 8 2025

...New AVIATION...

.KEY MESSAGES...
Updated at 152 AM PDT Wed Oct 8 2025

 - Cooler and cloudier weather today

 - Drizzle tonight through Thursday morning

 - Light rain chances increase Friday through Saturday morning for
the North Bay, Bay Area and East Bay

&&

.UPDATE...
Issued at 855 AM PDT Wed Oct 8 2025

Extensive stratus cloud cover persists across the inland valleys
of the Bay Area and Central Coast this morning. The inland regions
are expected to gradually clear out through the afternoon hours,
but the coastal region could remain socked in through the day. The
forecast remains on track with no changes necessary.

DialH

&&

.SHORT TERM...
Issued at 152 AM PDT Wed Oct 8 2025
(Today and tonight)

A weak upper level low that has lingered off the central coast the
previous few days has begun evolving into an open wave overnight and
will eventually be absorbed by a deepening trough to our north later
this afternoon. The pattern change in motion this morning will
result in inland temperatures today that will be 5-15 degrees cooler
than yesterday and up to 5 degrees cooler along the coast. A weak
surface trough out ahead of the first of numerous upper level trough
axis` passing through our area the rest of the week, will bring
areas of drizzle tonight through Thursday morning.

&&

.LONG TERM...
Issued at 152 AM PDT Wed Oct 8 2025
(Thursday through Tuesday)

The persistent troughing pattern through the extended forecast
period will keep temperatures around or below normal well into next
week. Rain chances continue primarily for the North Bay Friday into
early Saturday, with thunderstorm chances around 5% or less Friday
afternoon. Consensus is good wrt the overall pattern through the
weekend. Extended deterministic guidance has poor consensus on
the potential for widespread wetting rainfall for the beginning of
next week. ECMWF/Canadian models have strong signal for rain,
while the GFS has little to no rain in our area for that same time
frame. The NBM is clearly leaning on the ECMWF/Canadian
solutions, which seems reasonable attm. The difference being the
GFS deepens an upper level disturbance farther inland, while the
ECMWF/Canadian indicate a more plausible deepening of the system
just offshore and push it south along the coast, giving it more
time to pick up moisture along the way.

&&

.AVIATION...
(18Z TAFS)
Issued at 1042 AM PDT Wed Oct 8 2025

A southerly surge is supporting extensive stratus this morning
with high MVFR ceilings. These clouds are taking longer to clear
than expected, but signs of erosion are starting to show on the
satellite loop, and most terminals should be clear in the next
couple hours. Boundary layer averaged winds are from the south,
though the surface winds have a multiple forcing mechanisms that
will result in some erratic, gusty conditions through the
afternoon. The marine layer will expand considerably over the next
24 hours, bringing another round of stratus with higher ceilings
and a chance for drizzle across the Bay Area terminals Thursday
morning.

Vicinity of SFO...When will the ceilings break at SFO? That is the
pressing question for the 18Z TAFs. The trend in the high
resolution model guidance has been later and later and the
satellite and camera haven`t shown any improvement lately. There
is a decent chance that even 19Z is too early, and an amendment
may be needed. The other challenge today is wind direction. Winds
have been weak for the last 12 hours or so with aircraft soundings
reporting southerly winds just above the terminal. These winds
should filter down to the surface as the boundary layer becomes a
more unstable this afternoon. As the marine layer expands this
evening, returning ceilings will likely be VFR, though some
drizzle is possible particularly around 10-14Z.

SFO Bridge Approach...Similar to SFO

Monterey Bay Terminals...A sliver of dry air has weakened the
cloud deck and will contribute to an earlier clearing time today.
The wind direction forecast is low confidence with the southerly
surge and shifting surface winds today. The deepening marine layer
won`t be as saturated for these terminals, bringing less chance
for drizzle Thursday morning.

&&

.MARINE...
(Today through Monday)
Issued at 855 AM PDT Wed Oct 8 2025

Gentle to moderate SW winds will gradually shift back to a NW
breeze Thursday. Winds will increase to a strong NW breeze late
Saturday, building rough seas by Sunday. Disturbed conditions
with periods of rain and gusty winds are expected early next week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 PM PDT this afternoon for SF Bay N
     of Bay Bridge.

&&

$$

SHORT TERM...JM
LONG TERM....JM
AVIATION...Flynn
MARINE...Flynn

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