FXUS66 KMTR 191704
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
904 AM PST Mon Jan 19 2026

...New AVIATION...

.KEY MESSAGES...
Updated at 246 AM PST Mon Jan 19 2026

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

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

&&

.UPDATE...
Issued at 844 AM PST Mon Jan 19 2026

Once again, patchy fog is being reported in the North Bay 
Valleys, particularly in Sonoma County and eastern portions of 
Marin County. However, visibilities are forecast to improve within
the hour. Meanwhile, tule fog (dense at times) has pushed 
westward into the San Pablo/Suisun Bay, Delta, and interior East 
Bay Valleys this morning. This is mainly impacting places in and 
around Concord, Walnut Creek, Antioch, Brentwood, and Byron. 
Across this area, look for conditions to improve by late morning 
as surface temperatures begin to warm and allow for the fog to mix
out. Otherwise, no updates anticipated at this time. For more 
information, see the previous forecast discussions below. 

&&

.SHORT TERM...
Issued at 246 AM PST Mon Jan 19 2026
(Today and tonight)

Patchy fog is developing in the North Bay Valleys with intermittent 
reports of dense fog (1/4 statute mile visibility or lower) 
coming in from KSTS (Santa Rosa Airport) and KDVO (Novato/Gnoss 
Field Airport). Will hold off on a Dense Fog Advisory for now as 
the areas of dense fog are localized/not widespread on the webcam 
footage. If anyone is commuting in the North Bay Valleys, East Bay
Valleys, or along the San Pablo/Suisun Bay and Delta areas this 
morning, be aware of the potential for dense fog, be prepared for 
sudden changes in visibility, and remember to slow down. 

High pressure remains the name of the game. A ridiculously resilient 
ridge remains fixed over the West Coast with temperatures running 
anywhere from 5 to 15 degrees above normal for this time of year. 
High temperatures on Sunday were generally in the mid to upper 60s 
across the lower elevations of the Bay Area, upper 60s to low 70s 
across the higher elevations, and low to upper 70s across the 
Central Coast. The temperature distribution for today looks to be 
fairly similar with highs in the mid to upper 60s across the Bay 
Area and upper 60s to mid 70s throughout the Central Coast. Guidance 
shows a shallow (500 ft) marine layer developing tonight which may 
bring additional fog and low clouds to portions of the coastline 
tonight. Winds remain light and offshore through midweek.

&&

.LONG TERM...
Issued at 246 AM PST Mon Jan 19 2026
(Tuesday through Sunday)

Ridging sticks around through at least midweek before an upper level 
trough pushes in late Wednesday into Friday. This upper level trough 
will develop as a cut-off low and move southwards along the 
California coastline late this week. Unfortunately, this system 
looks to be dry with no rain expected from this system. PWAT 
values are between 0.7"-0.8" with a slightly stronger moisture tap
entering southern California (where models show the potential for
light rain). In the wake of this cut-off low, upper level ridging
redevelops over the West Coast this weekend into next week. Rain 
lovers should not fully despair yet as models do signal some 
potential for rain to return late January/early February. The 
ECMWF shows some potential for light rain in early February with 
deep upper level troughing pushing into the West Coast. Models 
have consistently showed something developing late January/early 
February but the timing continues to be pushed back. The timing of
the return of rain will become more clear as we get closer in 
time to late January/early February.

While we aren't expecting any rain with this upper level trough, it 
will bring in cooler air amd a return of more seasonal 
temperatures. High temperatures remain warm on Tuesday with highs
in the mid 60s to low 70s (approximately 5 to 10 degrees above 
normal). Temperatures cool into the upper 50s to mid 60s 
Wednesday into the weekend as the ridge breaks down and cooler 
air arrives with the upper level trough. As the ridge rebuilds
over the weekend, temperatures may warm by a few degrees but
overall remain seasonal in the low to mid 60s. Winds shift 
onshore mid to late week as the upper level low moves down the 
coastline but they will shift offshore again by the weekend as the
ridge rebuilds. Localized dense fog continues nightly across the 
interior valleys through the weekend with the potential for more 
fog to become more widespread across the interior valleys starting
Thursday night.

&&

.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.
&&

$$

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

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Prepared by Boulder-Creek.com Weather at: Mon Jan 19 12:30:03 PST 2026