885
FXUS66 KMTR 181854
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1054 AM PST Tue Nov 18 2025

...New AVIATION...

.KEY MESSAGES...
Updated at 1242 PM PST Mon Nov 17 2025

 - Scattered showers will gradually decrease through Tuesday
   morning before drier weather returns Tuesday afternoon.

 - Next system brings more beneficial type rain late Wednesday
   through Thursday.

&&

.UPDATE...
Issued at 1027 AM PST Tue Nov 18 2025

The upper level low is currently just off the coast of southern
CA. Skies should remain a mix of sun and clouds today with high
temperatures in the mid 40s to upper 50s for elevated areas, and
the upper 50s to low 60s elsewhere.

&&

.SHORT TERM...
Issued at 312 AM PST Tue Nov 18 2025
(Today and tonight)

Near term weather continues to be driven by the slow moving upper
level low pressure currently parked over the Central Coast. Enough
lingering moisture and lift are present around the upper low to
generate widely scattered showers. Interesting to watch KMUX radar
imagery early Tuesday morning with shower activity pivoting
counter-clockwise around the upper low with the heaviest shower
activity over the coastal waters. Freezing level is hovering
right around 5k so cannot rule out some wet snow flakes over the
higher peaks of the Central Coast this morning. Latest CAMS keep
these scattered showers through mid-morning, but primarily out of
the Bay Area and mainly over the Central Coast. By this
afternoon, overall drying will occur with fair weather CU behind
the departing upper level. Despite some drying and sunshine, today
will be seasonably cool with highs in the 50s to near 60 (40s
higher peaks).

Subsidence behind the departing low pressure system and shortwave
ridge overhead will lead to some clearing Tuesday night into early
Wednesday. Given the recent rain and ample low level moisture some
interior valley fog will be possible tonight.

&&

.LONG TERM...
Issued at 415 AM PST Tue Nov 18 2025
(Wednesday through Monday)

Dry weather holds through most of Wednesday, but temperatures
remain on the cool side again. Cold air and daytime heating will
likely lead to fair weather CU again.

The dry weather quickly comes to an end Wednesday thanks to an
active longwave pattern over the EPac. Another robust upper level
jet becomes amplified over the EPac Wednesday leading to another
round of cyclongensis off the West Coast. A surface low is
forecast to develop in the Gulf of AK Wednesday and then deepen as
it track east. The low will ultimately drag a cold front through
NorCal Thursday. Additionally, the amplified upper level jet will
help to cut-off another upper low off the CA Thursday into Friday.
The passing front and developing upper low will bring precip back
to the region. Rain is still on track to return to the N Bay
Wednesday night and then progress S and E early Thursday. Showers
will linger through Thursday night. While this front has some
moisture, the main tap isn`t overly robust despite it`s origin
back to near HI. PWATs are just shy of one inch. All that being
said, guidance has been trending slightly drier with total
rainfall Wednesday through early Friday. Still looking more
beneficial than hazardous to the region. Rainfall amounts will
generally be a tenth or two and up to three quarters of an inch N
Bay and coastal mountains. If the upper low over produces, the end
higher end of precip amounts (1 in 10 chc) would double those
rainfall amounts. One low confidence portion is the exact timing
of the front and its potential impact to the Thursday morning
commute.

Warming and drier conditions are expected to develop Friday and
over the weekend. Given another burst of rain, night and morning
fog will likely be the bigger weather impacts this weekend.

&&

.AVIATION...
(18Z TAFS)
Issued at 1054 AM PST Tue Nov 18 2025

Expect widespread VFR into the afternoon as cloud cover erodes
across the area. Expect light to moderate winds through the evening
before winds reduce into the night. Wind directions look to be
driven by local effects through the day, and winds will be more
variable into the night as they weaken. As a weak low pressure
center moves through the area, causing some southerly to easterly
winds overnight and into Wednesday morning with some spotty lower
CIGs. Slight chances for light rain will also more through the area
into the late morning, but these rains do not look impactful.

Vicinity of SFO...Skies are clearing with easterly winds looking to
turn westerly in the mid afternoon. These winds will weaken into the
night and turn southwesterly as scattered mid-clouds return. Expect
MVFR-level CIGs to return into early Wednesday as winds turn more
southerly, but these CIGs rise into that afternoon as light showers
move through the area and winds become southwesterly again.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Scattered mid-level clouds linger through
the day. Light winds turn more moderate and westerly in the mid
afternoon and last into the night before becoming light and
variable. SNS looks to be affected by moderate drainage winds from
the southeast into early Wednesday.

&&

.MARINE...
(Today through Sunday)
Issued at 1027 AM PST Tue Nov 18 2025

Light showers exit into the afternoon. Expect wave heights remain
elevated and winds remain fresh to strong with near gale force
gusts possible across the northern waters through late Tuesday.
Marine conditions briefly improve Wednesday as wave heights abate
and winds diminish. A weak system will arrive late Wednesday into
Thursday bringing a return of light rain and hazardous marine
conditions. Locally fresh to moderate winds and significant wave
heights between 10 to 15 feet are expected Thursday into the
weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 PM PST this evening for Pt Arena to
     Pt Reyes 0-10 nm.

     Small Craft Advisory until 3 AM PST Wednesday for Pigeon Pt to
     Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...Murdock
MARINE...Murdock

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, X, and YouTube at:
www.facebook.com/nwsbayarea
x.com/nwsbayarea
www.youtube.com/nwsbayarea