FXUS66 KMTR 171702
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
902 AM PST Sat Jan 17 2026

...New AVIATION...

.KEY MESSAGES...
Updated at 1205 AM PST Sat Jan 17 2026

 - Dry weather, cool mornings, and warm afternoons continue

 - Morning fog across the delta and interior valleys

&&

.UPDATE...
Issued at 837 AM PST Sat Jan 17 2026

Once again, the interior East Bay Valleys and West Delta are 
experiencing areas of dense fog. Currently, both Byron and Concord 
airports are reporting less than 1/4 mile visibility. Patchy fog 
also prevails in the North Bay Valleys with high cloud cover working 
in from the south. As surface temperatures warm, the fog is expected 
to gradually mix out; first across the North Bay and by midmorning 
or early afternoon across the West Delta and interior East Bay 
Valleys. We will continue to watch closely how these high clouds 
will affect afternoon temperatures, but largely should still be 
another warm day across much of the region this afternoon with high 
temperatures in the mid 60s to mid 70s (up to 80 degrees F in the 
higher terrain). Otherwise, no updates are anticipated this morning 
as the forecast remains on track.

&&

.SHORT TERM...
Issued at 1205 AM PST Sat Jan 17 2026
(Today and tonight)

Conditions are similar to last night, with a few subtle changes. 
First, the marine stratus has peeled off the coast. This is thanks 
to robust offshore flow. The SFO-WMC gradient is -12.3 mb, quite a 
bit stronger than most models have it analyzed. Mt. St. Helena is 
reporting ENE winds gusting as high as 47 mph tonight. This and 
several other mountain stations would actually be in Red Flag 
Criteria if the annual grasses were cured. This offshore gradient 
will weaken over the next 36 hours as both the strong surface high 
over the Rockies and the trough over California weaken. The other 
difference tonight is high clouds moving in from the south. These 
will help moderate both the min and max temperature by a degree or 
two and bring some color to the sunrise and sunset today. Otherwise 
it will feel very similar to yesterday.

&&

.LONG TERM...
Issued at 1205 AM PST Sat Jan 17 2026
(Sunday through Friday)

Sunday will be a rinse and repeat of Saturday. Expect a chilly 
morning, warm afternoon and some high clouds through the day. This 
pattern will stick around as the strong ridging that extends all the 
way to the jet stream will continue through the week. There is a 
chance for a short wave trough at 500 mb to bring some very light 
rain Thu-Fri, but it's looking more and more like that will just 
be a cloud maker. That little trough is important though. It's 
the first domino to fall in the gradual pattern change. The 500 mb
flow will likely become more zonal by next weekend. There's 
significant disagreement in the ensemble clusters after next 
weekend, but some solutions bring a legitimate troughing pattern 
and possible wet weather back for the last week of January. The 
00Z ECMWF ensemble IQR has between 1.0-2.5" of rain from the 27th 
to the 31st at SFO.

&&

.AVIATION...
(18Z TAFS)
Issued at 902 AM PST Sat Jan 17 2026

Stratus is clearing out across the interior East Bay valleys as the 
Tule Fog starts to mix out across the Central Valley. The far 
interior could remain socked in through the day but CCR should clear 
out later this morning and afternoon. Generally VFR conditions with 
high level clouds prevail through the day elsewhere, with 
predominantly gentle winds and a largely offshore flow across the 
interior, with a gentle onshore breeze for the coastal areas. 
Overnight, radiational fog develops across the North Bay valleys, 
including STS and APC, and the East Bay valleys, although confidence 
is low for impacts at LVK, CCR has a better chance for reduced 
visibilities and lowered ceilings overnight. High resolution 
models are also placing some possibility for fog or low stratus at
SJC later tonight, but this is a low confidence forecast at this 
time. 

Vicinity of SFO... VFR through the TAF period. A gentle offshore 
flow develops in the afternoon and evening hours. Otherwise, winds 
remain light and variable.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... VFR through the TAF period. Light and 
variable winds through the daytime, with breezy valley drainage 
winds developing overnight.

&&

.MARINE...
(Today through Thursday)
Issued at 837 AM PST Sat Jan 17 2026

Moderate to breezy northeast winds continue across the San Pablo
Bay, the delta, and through the Golden Gate through the weekend
while light northeast to north winds persist across the rest of
the coastal waters. Light seas continue into early next week
before the next round of long period swell arrives and brings
light to moderate seas in the mid week.

&&

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

$$

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

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Prepared by Boulder-Creek.com Weather at: Sat Jan 17 10:30:03 PST 2026