National Weather Service United States Department of Commerce

Tracking Winter Weather and Frigid Temperatures This Weekend

Another clipper will drop into the Northern Plains and Upper Midwest into Sunday with snow and gusty winds contributing to some areas of blizzard conditions and snow squalls. Impactful snowfall will occur up and down the East Coast Sunday extending from the western Florida Panhandle to Maine. Read More >

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012
FXUS66 KMTR 181125
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
325 AM PST Sun Jan 18 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1206 AM PST Sun Jan 18 2026

- Dry weather, cool mornings, and warm afternoons this week

- Morning fog possible across the Delta and interior valleys

&&

.SHORT TERM...
Issued at 1206 AM PST Sun Jan 18 2026
(Today and tonight)

High clouds continue to blanket the Bay Area and Central Coast
tonight. These elevated moisture is concentrated between 27,000 and
37,000 ft. The main impact of these clouds is reducing radiational
cooling to space. They do this indirectly by absorbing and re-
emitting thermal energy back to the surface. Valley temperatures are
between 1-5 degrees warmer than this time last night. However this
degraded cooling hasn`t been enough to stop the Tule Fog from
forming in the Central Valley. Dense fog is being reported from
Sacramento to Hanford, including the Sacramento River Delta and
surrounding areas. Concord has been reporting dense fog for several
hours, but no other airports in our cwa have joined in. The SFO-WMC
gradient is -8.2 mb, substantially weaker than 24 hours ago. This
is bringing much lighter offshore winds, with Mt. St. Helena now
gusting around 5 mph, vs nearly 50 mph last night. Outside of the
weaker mountain winds, today will be nearly identical to
yesterday. Expect a crisp morning with some localized fog,
colorful sunrise thanks to high clouds, warm afternoon with
filtered sunshine, and another great sunset. Enjoy the weather
today, it doesn`t get much better this time of year.

&&

.LONG TERM...
Issued at 1206 AM PST Sun Jan 18 2026
(Monday through Saturday)

The ridge is gradually weakening, but nice weather will continue
in the long term period. The 500 mb height is continuing to very
slowly lower following the near record of 5,900 m last Wednesday.
This trend will continue through the week, and it`s expected to
fall below 5,700 m by Friday. That`s near the daily average for
this time of year. A similar story is unfolding with the 850 mb
temperature, dropping from near record territory to near normal by
the end of the week. This is being caused by a trough over the
North Central Pacific spitting out a cut-off upper level low late
this week. All indications are that this system will have a very
weak surface reflection and will stay offshore through the
weekend, but it will take a bite out of the ridge. While it`s
still possible for a few drops to fall, the trend has been clear
that this system will not bring significant rain to the cwa. It
will, however, serve as a catalyst to usher in a more active
pattern the following week, which could bring us some long-
awaited rain for the last few days of the month.

&&

.AVIATION...
(12Z TAFS)
Issued at 317 AM PST Sun Jan 18 2026

Largely a persistence forecast this TAF round with mostly light
and variable winds and VFR conditions. High confidence in VFR with
the exception of the usual suspects under this flow regime (North
Bay and East Bay interior). Moderate confidence in localized FG
invof North Bay terminals and hazy conditions across the inland
East Bay through sunrise. Otherwise all terminals VFR through this
afternoon.

Vicinity of SFO...VFR. Light offshore flow regime results in light
NE winds at the terminal during the morning hours. Becoming
lighter and variable or turning more NW by the afternoon during
peak heating.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR. Light and variable winds with SE
drainage flow out of the Salinas Valley overnight tonight and
Sunday morning.

&&

.MARINE...
(Today through Friday)
Issued at 317 AM PST Sun Jan 18 2026

Gentle to moderate northeast to east breezes persist across the
San Pablo Bay, the Delta, and through the Golden Gate through
early next week while light to gentle northeast to north winds
continue across the rest of the coastal waters. Low seas continue
today, with a northwest swell building to 5 to 6 feet by early to
mid week.

&&

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

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...Behringer
MARINE...Behringer

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