FXUS66 KMTR 171743
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1043 AM PDT Mon Aug 17 2026

...New AVIATION...

.KEY MESSAGES...
Updated at 1201 AM PDT Mon Aug 17 2026

 - Shallower marine layer through midweek

 - Minor fluctuations in temperatures this week

&&

.UPDATE...
Issued at 925 AM PDT Mon Aug 17 2026

Water vapor imagery shows an elongated upper level trough off the
West Coast this morning, with a disturbance moving through this
trough off the Mendocino Coast. This disturbance is bringing 
plenty of mid and upper level cloud cover to Northern and Central 
California. Given this thick cloud shield, it is hard to see the 
inland extent of the marine layer. However, we are continuing to 
see ceilings at all of our terminals, except for Livermore, which 
is scattered at this time. In addition, the 12z KOAK sounding 
shows that is it still shows the marine layer at 1800 feet deep, 
and we once again saw some patchy drizzle along the immediate 
coast, with several locations, mainly around the Monterey
Peninsula and Bay, measuring 0.01 inches.

Given this blanket of high clouds, most locations were not as 
cool this morning as yesterday, and for that reason, we are 
running 2 to 4 degrees warmer than this time yesterday. However, 
this cloud cover is also going to limit our day time heating. 
Therefore, expect another day of below normal to near normal 
temperatures across the region. Currently forecast seems to be 
handling these trends well, so no update is planned at this time. 
Palmer

&&

.SHORT TERM...
Issued at 1201 AM PDT Mon Aug 17 2026
(Today and tonight)

Quiet weather today with little to no impactful weather expected 
through the next week. Temperatures today will be near or slightly 
below normal for this time of year with slightly more mild overnight 
lows to wake up to this morning than we've seen the last few days 
due to mid/high level cloud cover insulating radiative cooling. The 
mid to high level cloud cover will continue out ahead of a 
persistent troughing pattern over the EPAC. The additional cloud 
cover may impact daytime highs as well, limiting peak day heating 
somewhat. Some patchy fog and drizzle may be possible as well, 
especially right along the coastline.

&&

.LONG TERM...
Issued at 1201 AM PDT Mon Aug 17 2026
(Tuesday through Sunday)

Slight shifting in the persistent troughing over the EPAC and the
upper level ridging over the Four Corners region will result in 
subtle warming Tuesday and Wednesday, as the upper ridge pushes 
west slightly. The troughing pushes back to the east for the 
remainder of the week, cooling temperatures a few degrees. 
Overall, temperatures will be on the cooler side of normal for a 
majority of forecast period. There is no clear signal for a 
significant pattern change through the extended forecast.

&&

.AVIATION...
(18Z TAFS)
Issued at 1042 AM PDT Mon Aug 17 2026

Stratus is beginning to clear to the immediate coastline allowing 
for VFR conditions across the interior. However, coastal terminals 
may remain IFR/MVFR with only brief breaks in the low cloud cover 
this afternoon. High level clouds will persist today as well. 
Onshore winds increase this afternoon and remain gusty at times 
through early evening. Expecting an inland push of stratus late this 
evening and spreading into the inland valleys overnight. The 
greatest potential for LIFR is in the coastal terminals and KSTS 
early Tuesday morning. IFR/MVFR is most likely in the Bay Area 
terminals early Tuesday morning before scattering out by 18Z-20Z 
Tuesday. Onshore winds increase again by Tuesday afternoon. 

Vicinity of SFO...VFR. Onshore winds are forecast to increase by 
early this afternoon and will be gusty at times through early 
evening. IFR/MVFR ceilings return early Tuesday morning with 
weaker wind speeds, potentially variable at times Tuesday morning 
before increasing once again by the afternoon. 

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...LIFR at KMRY and MVFR at KSNS currently,
eventually becoming VFR at KSNS this afternoon with the potential
for KMRY to remain MVFR throughout the day. However, have KMRY 
scattering out by 20Z in the current TAF. Have LIFR/IFR conditions
returning this evening and potentially lowering into the night, 
however confidence is not great enough to include in the TAF at 
this time.

&&

.MARINE...
(Today through Saturday)
Issued at 925 AM PDT Mon Aug 17 2026

Winds gradually increase with a fresh to strong breeze developing
by late tonight and continuing 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 abating late 
week. 

&&

.FIRE WEATHER...
Issued at 1205 AM PDT Mon Aug 17 2026

Nocturnal drying through at least mid-week as the marine layer 
gradually compresses. Expect 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 to 3 PM PDT Tuesday for Pt Arena 
     to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...JM
LONG TERM....JM
AVIATION...RGass
MARINE...RGass

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Prepared by Boulder-Creek.com Weather at: Mon Aug 17 12:30:03 PDT 2026