FXUS66 KMTR 202153
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
253 PM PDT Thu Aug 20 2026

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

.KEY MESSAGES...
Updated at 253 PM PDT Thu Aug 20 2026

 - Seasonable to seasonably cool temperatures through early next week

 - Elevations above about 1000 feet will remain warm and dry

&&

.SHORT TERM...
Issued at 253 PM PDT Thu Aug 20 2026
(This evening through Friday night)

The marine layer retreated to the coast as expected and high clouds 
continue to stream overhead. Expect these conditions to hold for a 
few more hours, before the marine layer and associated stratus begin 
to creep inland. Models suggest the marine layer is suppose to be 
around 1000ft tonight, which should limit its expansion into the 
South and East Bay valleys. Will need to keep an eye on its arrival 
and the actual footage as the picture from space has indicated a 
slightly deeper marine layer the past few mornings. Nonetheless, for 
those that do get the stratus, look for cloudy skies, coastal 
drizzle, and potentially patchy fog through the morning hours. Low 
clouds will either erode or retreat to the coast, while high clouds 
continue overhead. The cooling trend continues into tomorrow, with 
high temperatures being a few degrees lower than today. 

&&

.LONG TERM...
Issued at 253 PM PDT Thu Aug 20 2026
(Saturday through next Wednesday)

No major changes to the long term forecast. A stout upper level 
ridge will remain over the Desert Southwest while an upper low 
tracks into the PacNW and southwestern Canada. We'll likely be in 
some form of weak troughing to quasi zonal flow during this time 
period, with temperatures cooling through Saturday and then 
moderating for the rest of the forecast period. Drier air works 
its way into the upper levels across at least the North Bay, which
might limit the stratus up there. Looking toweards the end of the
period, the strong dome of high pressure tries to slighlty build 
towards us. High temperatures should increase by a few degrees in 
response to this. 

&&

.AVIATION...
(18Z TAFS)
Issued at 1211 PM PDT Thu Aug 20 2026

Stratus has retreated to the coastline with most terminals in VFR 
and a parade of high clouds cruising overhead. HAF is the exception 
as they may have a brief scattering period this afternoon before 
developing IFR ceilings again. Typical onshore breeze pattern 
persists through the TAF period with an increase this afternoon. The 
marine layer returns this evening with a mixture of MVFR, IFR, and 
LIFR ceilings impacting coastal sites as early as sunset and inland 
sites around midnight. Medium confidence on the ceiling forecasts 
for LVK and SJC as the marine layer is expected to compress slightly 
overnight which may impact ceiling heights as well as coverage.

Vicinity of SFO...Onshore winds increase through the day with VFR
conditions prevailing during most of the afternoon. Borderline 
MVFR-IFR ceilings roll in around sunset tonight and persist until
late morning Friday. Westerly winds decrease through the 
overnight hours and increase as stratus clears tomorrow morning.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR through the afternoon with west to 
northwest winds increasing to around 10 kt. IFR ceilings impact 
both SNS and MRY around sunset time and drop to LIFR overnight as 
the marine layer compresses. This compression will impact 
visibility due to mist/drizzle. Conditions will gradually improve 
by late Friday morning. Medium confidence on exact timing of LIFR
conditions.

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 253 PM PDT Thu Aug 20 2026

Northwest moderate to fresh breezes persists into the weekend with
higher winds expected near the coastal jet regions of Point Reyes
and Point Sur. Occasional strong gusts are possible across the
outer  waters and coastal jet areas through Saturday. Wind driven
seas  remain slight at the coastline and quickly build to moderate
across  the outer waters through the weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Friday for Pt Arena to Pt 
     Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.

     Small Craft Advisory until 9 PM PDT this evening for Pigeon Pt 
     to Pt Pinos 0-10 nm.

     Small Craft Advisory from 11 AM to 9 PM PDT Friday for Pigeon Pt 
     to Pt Pinos 0-10 nm.

     Small Craft Advisory until 3 AM PDT Saturday for Pt Pinos to Pt 
     Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...KR
LONG TERM....KR
AVIATION...Navarrete
MARINE...Navarrete

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Prepared by Boulder-Creek.com Weather at: Thu Aug 20 16:30:02 PDT 2026