700
FXUS66 KMTR 180416
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
916 PM PDT Mon Aug 17 2026

...New UPDATE, MARINE...

.KEY MESSAGES...
Updated at 428 PM PDT Mon Aug 17 2026

 - Slight warming trend through Wednesday

 - Marine layer remains compressed through mid week

&&

.UPDATE...
Issued at 914 PM PDT Mon Aug 17 2026

Stratus has begun to push inland with less coverage expected than
last couple nights as the marine layer depth begins to gradually
decrease with increasing influence of the upper level ridging to
our east the next couple of days. Overnight lows will once again
be mild with mid/upper level cloud cover continuing to stream
across our area from southwest to northeast. Temperatures Tuesday
will be slightly above normal, the subtle warmup will continue
Wednesday before moderating back closer to or slightly below
normal by Thursday.

&&

.SHORT TERM...
Issued at 200 PM PDT Mon Aug 17 2026
(This evening through Tuesday night)

Water vapor imagery continues to show an elongated upper level
trough off the West Coast this afternoon, with the parent low
centered near 32.5 North and 137.5 West. There are several
disturbances moving around this trough, including the one lifting
across southwest Oregon that brought all of the high cloud cover
to Central and Northern California today. Water vapor imagery also
shows high pressure over the Desert Southwest, with California
remaining between the two large scale features, with relatively
moist southwesterly flow aloft over us. Unfortunately, all of
moisture is in the upper atmosphere in the form of high clouds.
There has been enough breaks in these clouds though that
our daytime temperatures today are warming more than I initially
gave them credit for. In fact, most locations are running 3 to 6
degrees warmer today over yesterday. That is in part to the warmer
start to the day, but also the combination of increasing 850 mb
temperatures, a compressing marine layer, and then sunshine. The
question now is whether or not there will be enough clouds to be
another insulating blanket tonight? Looking at the IR imagery,
think this is a plausible solution, and expect mild conditions
once again tonight. The marine layer will return again tonight,
but should be shallower (around 1500 feet), and not be quite as
widespread as this morning.

The upper level ridge, despite being dirty, will be the dominate
weather feature for Tuesday and Tuesday night, helping to
continue to minor warming trend, especially across the inland
areas. Despite the minor warming trend, daytime temperatures will
remain near to below normal through for most areas, with just the
far inland areas being above normal. The marine layer will also
start to compress, with more patchy fog possible during the late
night and early morning hours.  Palmer

&&

.LONG TERM...
Issued at 200 PM PDT Mon Aug 17 2026
(Wednesday through next Sunday)

This upper level ridge will remain our more dominate weather
feature at least Wednesday and potentially now into Thursday.
Therefore, expect inland areas to potentially see another degree
or two of warming on Wednesday, with little change for Thursday,
while coastal areas only see minor fluctuations, as a shallow
marine layer lingers along the coast.

The upper level low currently near 32.5 North and 137.5 West will
finally lift for Friday before moving into the Pacific Northwest
for the weekend. This will once again bring a deeper marine layer,
stronger onshore winds, and cooler conditions to the Bay Area and
Central Coast once again. That being said, the parent trough will
remain off the California Coast as another upper level low
replaces this first one. While the details are still not entire
clear on where this secondary parent low will set up, it will keep
California with south or southwesterly flow aloft through the
first part of next week. The East Pacific also looks to get active
with a series of easterly waves during this time. This could make
things a little more interesting around here, should something
try to form and slip north around the edge of the ridge. At this
point in time, that does not look likely, but can`t fully rule it
out either. Needless to say, this is something that will bears
watching. For now though, expect continued dry through the period.
Palmer

&&

.AVIATION...
(00Z TAFS)
Issued at 428 PM PDT Mon Aug 17 2026

Patchy MVFR-IFR stratus lingers at the immediate coast with the rest
of the region reporting VFR conditions with high clouds. Moderate
onshore pattern breezes will persist into the afternoon and evening
hours. This evening and overnight, generally IFR-LIFR stratus is
expected to make its way inland and impact most terminals, with
patchy fog possible and a low to moderate confidence of impacts to
LVK. Stratus will mix out Tuesday morning with gentle to moderate
onshore breezes resuming in the afternoon.

Vicinity of SFO... VFR with high clouds and moderate northwest
breezes persist through the evening hours. Winds will diminish late
in the evening with MVFR-IFR stratus developing overnight, mixing
out on Tuesday morning with breezy northwest winds resuming in the
afternoon. Low confidence for stratus development late Tuesday
evening before the end of the TAF period, which doesn`t improve much
after the end of the TAF period as the terminal area sits at the
edge of where high resolution model output paints the stratus
deck.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... VFR conditions will make way to returning
IFR-LIFR stratus through the next couple of hours. LIFR conditions
will develop overnight with mixing out expected through Tuesday
morning, with some uncertainty on clearing times. Moderate
confidence that MRY will scatter out sometime Tuesday afternoon.
Moderate northwest to west winds will continue through the evening
hours, turning light overnight before resuming Tuesday afternoon.

&&

.MARINE...
(Tonight through next Sunday)
Issued at 914 PM PDT Mon Aug 17 2026

A fresh to strong northwest breeze will develop tonight and
persist through the end of the forecast period. Locally stronger
winds are possible in the coastal jet regions north of Point Reyes
and along the Big Sur coast. Seas build to 7 to 9 feet by Tuesday
and Wednesday before subsiding later in the week.

&&

.FIRE WEATHER...
Issued at 200 PM PDT Mon Aug 17 2026

The marine layer will gradually compress over the next 24 to 36
hours, as high pressure builds over the region. As a result, nocturnal
drying will be possible through at least mid-week for the higher
elevations, with more widespread fair to moderate recoveries
developing over the higher elevations, especially in and around
the Timber Fire.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 AM Tuesday to 3 AM PDT Wednesday for
     Pt Arena to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...Palmer
LONG TERM....Palmer
AVIATION...DialH
MARINE...DialH

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