FXUS66 KMTR 190527
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1027 PM PDT Mon May 18 2026

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

.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


&&

.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 
out.
&&

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

Currently VFR at all terminals. High confidence in VFR and diurnal 
winds prevailing through the TAF period. Winds may become calm 
and/or light and variable overnight.

Vicinity of SFO...Currently VFR with westerly flow. High confidence 
in VFR and diurnal winds prevailing through the TAF period. Westerly 
winds will continue to diminish with the potential to become calm 
and/or light and variable overnight. 

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Currently VFR and calm at MRY and VFR with 
northerly flow at SNS. High confidence in VFR and diurnal winds 
prevailing through the TAF period.

&&

.MARINE...
(Tonight through next Sunday)
Issued at 932 PM PDT Mon May 18 2026

Conditions will continue to improve tonight as northerly breezes
continue to diminish. Rough seas will prevail in the outer waters
with moderate seas in the inner waters. Hazardous conditions for
small craft will persist through the week across the northern
outer waters due to rough seas and strong northerly breezes.

&&

.FIRE WEATHER...
Issued at 1251 PM PDT Mon May 18 2026

Gusty north to northeast winds will continue through this
afternoon before easing tonight into tomorrow. Peak gusts between
35 to 45 mph are still possible across the higher elevations into
this evening. Daytime humidity retention remains poor with most
sites staying around 10-25% across the interior and higher peaks
with limited overnight recoveries. Winds ease by Tuesday but fire
weather concerns will linger through late week as light offshore
flow continues and daytime humidities remain poor.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory until 3 AM PDT Tuesday for CAZ506.

PZ...Small Craft Advisory until 3 AM PDT Tuesday for Pt Arena to Pt 
     Reyes 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

     Small Craft Advisory until 9 PM PDT Wednesday for Pt Arena to Pt 
     Reyes 10-60 NM.

     Small Craft Advisory until 9 AM PDT Tuesday for Pigeon Pt to Pt 
     Pinos 10-60 NM.

&&

$$

SHORT TERM...KR
LONG TERM....KR
AVIATION...Sarment
MARINE...Sarment

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Prepared by Boulder-Creek.com Weather at: Tue May 19 04:30:02 PDT 2026