625
FXUS66 KMTR 052104
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
204 PM PDT Sun Oct 5 2025

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

.KEY MESSAGES...
Updated at 203 PM PDT Sun Oct 5 2025

 - Warmer and drier conditions through midweek, with moderate
   offshore wind expected through Tuesday in the higher elevations

 - Unsettled weather returns late in the upcoming week

&&

.SHORT TERM...
Issued at 203 PM PDT Sun Oct 5 2025
(This evening through Monday)

Mostly clear sky conditions have returned to the region this
afternoon with temperatures forecast to peak in the 60s near the
immediate coast, lower 70s just inland away from the coast, and the
low 70s to lower 80s across the interior. This is a result of the
offshore flow in the higher elevations and building high pressure
over the eastern Pacific. However, troughing persist across the
Intermountain West with a cut-off low expected to develop overnight
just west of the Bay Area.

Low clouds and/or patchy fog are forecast to return back to the
coast and coastal adjacent inland valleys as the marine layer will
likely compress to around 1,000 feet in depth. The aforementioned
cut-off low will aid in increased offshore winds in the higher
elevations overnight and into Monday morning, being the strongest
over the North Bay and East Bay. Thus, the strength off the offshore
flow may limit low clouds and fog potential tonight and into Monday
morning.

Temperatures will warm into the upper 60s to lower 80s inland way
from the immediate coast with upper 80s across the interior on
Monday afternoon.

&&

.LONG TERM...
Issued at 203 PM PDT Sun Oct 5 2025
(Monday night through next Saturday)

Warm conditions will persist into Tuesday afternoon (similar to
those on Monday), yet onshore flow is expected to cool temperatures
near the coast. By Wednesday, onshore winds will return to much of
the region and cool temperatures to near seasonal averages.

There remains much uncertainty from Thursday and into the upcoming
weekend. There is fairly decent confidence that temperatures will
cool in response to an upper level through approaching and/or moving
inland over the Pacific Northwest. However, the confidence of
receiving rainfall remains the big question beginning Friday. The
greatest potential of seeing any rainfall will be over the North Bay
and in the Santa Cruz Mountains as a cold front moves through the
region.

From the previous forecaster: "The biggest question in the forecast
is if this moisture will reach the Bay Area before the cold front
arrives and stops its forward progress. If it does, the front will
have a very juicy atmosphere to lift, potentially bringing up to an
inch of rain to parts of the Bay Area. If it doesn`t, the offshore
winds all week will leave a drier than normal air mass, severely
limiting rain potential. To demonstrate the uncertainty, the NBM 72
hour precipitation spread (10th-90th percentile) paints a stark
contrast. The wet scenario would bring 1.7" of rain to NW Sonoma
County through the weekend, while the dry scenario wouldn`t bring a
drop. Those outcomes are both equally likely at the moment, so don`t
put too much faith in the forecast details. All we can say now is
the next chance for rain arrives late next week, but we can`t yet
say how much will fall."

&&

.AVIATION...
(18Z TAFS)
Issued at 1048 AM PDT Sun Oct 5 2025

Generally light winds are most terminals today under VFR, with
exception of Half Moon Bay where the cigs are hanging on a longer
than anticipated and the vsby is lower than expected at this time.
Winds will turn onshore and up valley at all locations by the
early afternoon hours, which will bring up the humidity and give
the chance for some low elevation clouds to pop up here and there.
As such, you`ll see "FEW" for cigs in some of the coastal TAFs,
like MRY. Winds will ease in the early evening then make a shift
overnight to become offshore. At this time the expectation is the
offshore winds will bring a drier air mass in and clear out cigs.
This pattern should remain into mid morning Monday. With the
offshore winds downsloping at HAF, opted to add in some gusts
there for a time too.

Vicinity of SFO...Just a few clouds lingering around this morning
due to residual moisture from overnight. However, with winds
backing to the WNW, moisture content will increase causing
humidity to plateau for the day. As such, opted to keep a "few"
deck in through the day and into the evening. Offshore flow will
develop overnight, bringing in a drying air mass. This will clear
out clouds and allow for full SKC in the overnight and early
morning hours. Look for onshore winds try and come back Monday
late afternoon into early evening. This could bring back a few
clouds.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...SNS will benefit from being inland today
with SKC and generally light to moderate winds. MRY is the
challenge as higher humidity is lingering just offshore. With
onshore winds developing this afternoon, the question is whether
or not it will push clouds into the terminal. For now have hedged
with a "SCT" deck this afternoon. If we get a stronger push, this
could become BKN or OVC. That said, models indicate an Otter Eddy
developing in the Bay which could bring SW winds to the terminal,
causing some downsloping winds off of Del Monte forest helping to
dry the air out and dissipating the clouds. Either way, by sunrise
Monday, offshore winds will develop, dry the air mass out, and
bring full P6SM SKC for a portion of Monday morning.

&&

.MARINE...
(Today through Friday)
Issued at 428 AM PDT Sun Oct 5 2025

Winds continue to diminish across the waters. Gentle breeze
today, becoming light through the rest of the week. Seas abate
with the wind through the week. Next upper level disturbance
anticipated by the end of the week with winds increasing across
the outer waters by Thursday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 PM PDT this afternoon for Pt Arena
     to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...RGass
LONG TERM....RGass/Flynn
AVIATION...BFG
MARINE...BFG

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