Technical NOAA Weather Discussion

FXUS66 KMTR 120750
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1250 AM PDT Tue May 12 2026

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

.KEY MESSAGES...
Updated at 1216 AM PDT Tue May 12 2026

 - Gradual cooling trend develops today through midweek

 - Warming and drying trend midweek and beyond

&&

.SHORT TERM...
Issued at 1216 AM PDT Tue May 12 2026
(Today and tonight)

The pattern shift discussed on yesterday's AFD is upon us. A quick
snapshot of the longwave pattern over the West shows a ridge
sneaking off to the east and settling over the Desert SW and
knocking on CA is an upstream upper trough and associated cut-off
low. Onshore flow plus lower 500 mb heights equals a deep marine
layer presences this morning. Satellite fog product shows a decent
marine layer with way more inland intrusion than 24 hours ago.
Marine layer depth will vary from 1000-1500 feet this morning.
Light mist or drizzle will be possible along the immediate
coastline through this morning.   

Deeper marine layer and onshore flow will lead to a later 
clearing time of inland stratus for Tuesday. The coast on the 
other hand may not see much in the way of clearing today. 
Noticeable cooldown for Max Temps today bringing readings closer 
to seasonal averages. Max Temps 60s to 70s coast/bays and 70s to 
lower 90s interior. 

If we follow the trend is your friend logic: the upstream upper 
low has been trending more north and continues to do so. As such, 
the chance for widespread drizzle and/or light rain has now been 
removed from the forecast late Tuesday night into Wednesday. That 
being said, still expecting another push of marine stratus 
overnight. 

&&

.LONG TERM...
Issued at 1216 AM PDT Tue May 12 2026
(Wednesday through Monday)

The upper low will sweep through Oregon during the day on
Wednesday. While the forecast has trended drier temperatures will
still be on the cool side. Wednesday will be coolest day of the
forecast. Additionally, expect some breezy onshore winds through
out the day. Winds will be strongest along the coast and inland 
gaps/passes.  

Quiet weather returns for the second half of the work week and 
into the weekend with zonal flow, warming temps, night/morning 
clouds.

&&

.AVIATION...
(06Z TAFS)
Issued at 949 PM PDT Mon May 11 2026

Stratus has brought MVFR to IFR cigs to the coast and some interior 
North Bay valleys and the northern Salinas Valley. Models trend with 
the marine layer at 1000 feet, but it might get closer to 1200 feet 
tonight. This will bring yet another night of low clouds and 
potentially visibility. Trended the forecast to account for the 
inland push in the North Bay, while East and South Bay terminals 
hold similar timing to the previous TAFs. Stratus should burn off by 
mid to late morning, breezy onshore flow is expected tomorrow 
afternoon and evening. Medium to high confidence in the forecast. 

Vicinity of SFO...Breezy westerly winds should begin to decrease 
within the next hour or so becoming less than 10kt for the overnight 
hours. The stratus looms just west of the terminal, with VFR 
conditions prevailing. The onset of stratus should occur later 
tonight, but there are also some models showing the stratus arriving 
closers to 12Z, with low clouds mixing out by 17-20Z. Breezy 
westerlies return tomorrow afternoon, with gusts up to 21kt by 21Z 
and 30kt closer to 30Z. Breezy winds look to last into the evening 
with gusts to 20-25kt potentially lasting through 6Z. Medium 
confidence in the forecast. 

SFO Bridge Approach...Similar to SFO. 

Monterey Bay Terminals...The actual Bay is socked in with stratus 
which is making a good inland push. KMRY has already succumbed to 
the stratus, with cigs falling to LIFR. KSNS is following suit, with 
another night of low cigs and vis for them and other terminals. Most 
guidance stratus mixing out by mid to late morning, with the 
exception being at KMRY. There is uncertainty if we'll be able to 
fully clear, or if we'll get a few pockets of sunshine between 18-
23Z. Medium to high confidence in the forecast. 

&&

.MARINE...
(Tonight through next Sunday)
Issued at 949 PM PDT Mon May 11 2026

Occasional strong gusts continue through tonight across the far
northern outer waters. Otherwise, a moderate to fresh northwest
breeze will continue over the waters through midweek. Seas subside
but remain moderate with 4 to 6 foot seas through midweek. Winds
increase and seas build starting mid-week with gale force winds
and wave heights in excess of 10 feet likely starting Friday and
continuing through the weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this 
     evening for Pt Arena to Pt Reyes 0-10 nm-SF Bay N of Bay 
     Bridge.

&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...KR
MARINE...Kennedy

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Prepared by Boulder-Creek.com Weather at: Tue May 12 04:30:03 PDT 2026
From the National Weather Service