545
FXUS66 KMTR 080855
AFDMTR

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

...New SHORT TERM, LONG TERM...

.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

&&

.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...
(06Z TAFS)
Issued at 1021 PM PDT Tue Oct 7 2025

The low cloud will likely return this evening for most terminals
and has already snaked into some valleys. A most terminals,
bringing with it MVFR to IFR CIGS, though pockets of LIFR could be
possible in addition to reduced VIS. The marine layer should be
around 1000-2000ft by tomorrow morning, thus the stratus may be
able to penetrate into the East and South Bay terminals. Expect
inland clouds to retreat quickly, while clouds closer to the coast
either hold or clear out by late morning or early afternoon. High
clouds should start to stream in during the afternoon. Guidance
continues to show coastal drizzle late Wednesday night into
Thursday morning.

Vicinity of SFO...VFR conditions should prevail through the evening
hours, with stratus sneaking back into the TAF site later in the
period. Most guidance has stratus returning around the 9-12UTC mark,
and favors MVFR cigs, though a few suggest the possibility of IFR
after sunrise. Confidence was too low to carry IFR cigs for any
period, thus hinted at the possibility of it. The question then
becomes, how fast will SFO clear out? Uncertainty remains with a lot
of guidance favoring mid to late afternoon. Opted to go with the
more pessimistic outlook with MVFR cigs clearing sometime between
22UTC Wed or closer to 0Z Thu. Guidance shows lower cigs trying to
return again after 9Z Thu. Coastal drizzle may be possible.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...The southern half of Monterey Bay is clear
with VFR conditions prevails. Stratus continues to hug around Santa
Cruz County and the northern part of the Bay, and will likely hold.
Tonight, stratus should return to the Monterey Bay terminals, likely
and should start to sneak in over the next few hours. Given last
night`s stratus and the model guidance, opted to go with IFR
conditions at KMRY and KSNS, with perhaps a few bouts of LIFR
conditions if the cigs drop substantially and fog develops once
again. Conditions should clear out shortly by late morning, but some
guidance shows MVFR cigs holding until 21Z. Medium confidence on the
clearing time, medium to high confidence on lower CIGS and VIS for
tonight.

&&

.MARINE...
(Today through Sunday)
Issued at 848 AM PDT Tue Oct 7 2025

Expect mostly light to moderate winds accompanied by low to
moderate seas will prevail through early Wednesday before winds
begin to build in the northern outer waters. Winds and seas
continue to increase in the mid week and again into the next work
week. Drizzle chances affect the waters Wednesday and Thursday
with chances for light rain affecting the northern waters late
Thursday through early Saturday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&

$$

SHORT TERM...JM
LONG TERM....JM
AVIATION...KR
MARINE...CW

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