National Weather Service United States Department of Commerce

Lake-effect Snow and Whiteout Conditions in the Great Lakes Region; Below-average Temperatures in the East

Heavy lake-effect and lake-enhanced snow will persist downwind of the Great Lakes and produce some whiteout conditions that could cause difficult travel conditions. A coastal low will produce moderate to heavy snow over parts of southern and eastern New England into the afternoon. Below average temperatures are expected across the eastern U.S., particularly with chilly morning temperatures. Read More >

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242
FXUS66 KMTR 192031
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1231 PM PST Mon Jan 19 2026

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

.KEY MESSAGES...
Updated at 1230 PM PST Mon Jan 19 2026

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

- Morning fog across the Delta, North Bay Valleys, and interior
East Bay Valleys

&&

.SHORT TERM...
Issued at 1230 PM PST Mon Jan 19 2026
(This evening through Tuesday)

Very little change in day to day conditions anticipated through mid
week. A ridge of high pressure remains just off of the Pacific coast
that will continue to result in temperatures 5-10 degrees above
average (up to 15 in the higher terrain). Overnight, we are
expecting patch to areas of fog in the North Bay Valleys while tule
fog (dense at times) is forecast to advect westward into the
interior East Bay Valleys and Delta again either late tonight or
into Tuesday morning. If driving or commuting in these areas; be
aware of the potential for dense fog and be prepared for sudden
changes in visibility, remember to slow down, and use your low beam
headlights.

Expecting a slight cool down on Tuesday as more widespread high
clouds stream over the region, but only by a few degrees. Where
mostly sunny sky conditions prevail, afternoon temperatures will
warm into the mid 60s to lower 70s across the Central Coast and low
to mid 60s elsewhere. That said, where fog lingers into late morning
or early afternoon, expecting temperatures to only reach the upper
50s.

&&

.LONG TERM...
Issued at 1230 PM PST Mon Jan 19 2026
(Tuesday night through next Sunday)

Dry conditions look to persist through much of the extended
forecast. An upper level trough will develop over the north central
Pacific between Tuesday night and Wednesday. A cut-off low will
develop within that trough and move southward just off of the Bay
Area/Central Coast, resulting in slightly cooler conditions and
cloudier skies through late week. Thus, the greatest potential for
rain will be across southern California and along the Santa Lucia
Range on Thursday as a deeper plume of moisture advects inland to
the south. However there is about a 20% probability of seeing
greater than 0.01" and less than a 10% chance of that area seeing
0.10" over that area.

A weak upper level ridge is forecast to develop by this weekend and
into early next week. As a result, a slight warming trend is
forecast, but not as warm as what we have been the past week. Longer
range guidance continues to push back our next potential widespread
rainfall. It is not until late January or early February that we
forecast widespread rain to return to the region.

&&

.AVIATION...
(18Z TAFS)
Issued at 903 AM PST Mon Jan 19 2026

Fog and stratus continue to mix out across the interior East Bay
valleys with lingering impacts at CCR for the next couple of hours.
Winds will remain light to gentle with a weak onshore breeze near
the coast and offshore winds persisting inland. The TAF sites remain
VFR through the day, with fog and stratus return to the North and
East Bay valleys tonight with haze expected at LVK. High resolution
model data depicts some chance for stratus development near LVK and
in the San Francisco Bay tonight, but this is a low confidence
forecast at this time.

Vicinity of SFO... VFR through the day. High resolution model output
is attempting to place a patch of stratus within the southern San
Francisco Bay, but impacts to the terminal are not expected. Winds
remain light with offshore flow lingering through the morning until
mild onshore flow develops this afternoon.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... VFR through the TAF period. Light north to
northwest winds through the afternoon, with breezy valley drainage
winds developing overnight.

&&

.MARINE...
(Today through Saturday)
Issued at 844 AM PST Mon Jan 19 2026

Light to gentle northerly breezes persist across the waters this
week. Slight increase in winds over the outer waters by late week
as the large scale weather pattern begins to shift. Moderate
period northwesterly swell enters the waters mid week, peaking
Tuesday night into Wednesday morning.

&&

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

$$

SHORT TERM...RGass
LONG TERM....RGass
AVIATION...DialH
MARINE...DialH

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