FXUS66 KMTR 191727
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1027 AM PDT Tue May 19 2026

...New AVIATION...

.KEY MESSAGES...
Updated at 1026 PM PDT Mon May 18 2026

- Diurnally driven winds, with onshore winds during the afternoon 
   and early evening.  

- Above normal temperatures continue through midweek with seasonal 
  temperatures returning late week

&&

.UPDATE...
Issued at 914 AM PDT Tue May 19 2026

Clear skies across the region this morning with much lighter winds 
compared to this time yesterday. Temperatures across the lower 
elevations are running up to 10 degrees cooler than they were 
yesterday morning. Oppositely, temperatures across the higher 
elevations are running warmer than they were yesterday morning. 
Highs today will be in the 80s across the interior and 60s to 70s 
along the coast. Higher end forecasts suggest some potential for 
high temperatures to reach the low 90s across interior hot spots 
(North Bay valleys, East Bay hills, southern Santa Clara Valley). 

&&

.SHORT TERM...
Issued at 1026 PM PDT Mon May 18 2026
(Tonight through Tuesday)

The forecast appears to be on track, with broad upper level 
troughing holding over much of the western U.S. while high pressure 
builds over the eastern Pacific. The good news, is that our breezy 
offshore winds have eased substantially leaving us with fairly calm 
weather in return. Tonight, skies will remain clear and temperatures 
will generally fall into the 50s for the valleys, perhaps upper 40s 
for some coastal sites and the southern Salinas Valley. At higher 
elevations, a thermal belt will exist as temperatures fall into the 
mid 50s to low 60s and may still have some northerly winds. For 
those in the valleys, winds will generally be light and variable.

Tomorrow, another warm day will be on tap. The question will be, how 
do the temperatures pan out? Offshore flow won't be as prevalent, 
which means there could be less of a downsloping / warming of the 
air affect. But, that upper level high slowly creeps towards us and 
the marine layer is essentially negligible. Opted to blend a bit of 
the observations from Monday to the NBM giving us a similar 
forecast, to what occurred yesterday. The interior Bay Area valleys 
should make it into the 80s, perhaps near 90 degrees, while coastal 
communities experience a tighter gradient of highs in the 60s to low 
70s. The San Francisco Peninsula should be similar, with the Pacific 
side having temps range from the mid 60s to low 70s, while the Bay 
side ranges from the upper 70s to mid 80s. And finally the Central 
Coast, interior locations rise into the mid 70s to mid 80s, while 
coastal communities vary from the mid 60s to the low 80s. 

&&

.LONG TERM...
Issued at 1026 PM PDT Mon May 18 2026
(Tuesday night through next Monday)

No major changes to the extended forecast. Upper level troughing 
looks to keep hold over the western US through at least Wednesday, 
with that Pacific high slowly peeking into northern CA. This should 
bring a return of onshore flow to the region and eventually the 
marine layer. Warm weather looks to linger through at least 
Wednesday, with Thursday potentially seeing a slight change in 
temperatures if the marine layer develops. Guidance for Thursday 
caps it at 500ft at best, with the marine layer getting to 1000ft by 
Friday. The marine layer appears to better establish itself Friday 
night into Saturday, likely getting to around 1000ft again. Will 
need to keep an eye on this as it will affect how temperatures pan 

&&

.AVIATION...
(18Z TAFS)
Issued at 1021 AM PDT Tue May 19 2026

VFR will prevail the remainder of today and tonight with a chance
of MVFR/IFR cigs developing around sunrise Wednesday. Light and
variable winds this morning become light but steady onshore this
afternoon and evening.

Vicinity of SFO...VFR is expected through today and tonight with a
slight chance of MVFR cigs developing around sunrise Wednesday
with confidence too low for mentioning in the TAF attm.

SFO Bridge Approach...Similar as SFO.

Monterey Bay Terminals...VFR will prevail today and tonight with a
chance of MVFR/IFR cigs developing around sunrise Wednesday
morning. Expect light and variable to light onshore winds through
the TAF period.

&&

.MARINE...
(Today through Sunday)
Issued at 914 AM PDT Tue May 19 2026

Fresh northerly breezes will continue over the northern outer
zones  through tomorrow with hazardous conditions through Thursday
morning.  Wave heights increase again on Thursday with increasing
northwest  swell that eases for the end of the weak into the
weekend.

&&

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

&&

$$

SHORT TERM...KR
LONG TERM....KR
AVIATION...JM
MARINE...JM

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Prepared by Boulder-Creek.com Weather at: Tue May 19 12:30:03 PDT 2026