FXUS66 KMTR 130745
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1245 AM PDT Wed May 13 2026

...New KEY MESSAGES, SHORT TERM, LONG TERM...

.KEY MESSAGES...
Updated at 1200 AM PDT Wed May 13 2026

 - Cooling trend continues today 

 - Warming and drying trend resumes Thursday through the weekend

&&

.SHORT TERM...
Issued at 1204 AM PDT Wed May 13 2026
(Today and tonight)

A disjointed marine layer is trying to reform overnight per
satellite fog product. Where it is reforming it's rather deep at
1500-2000 ft. The complicating factor in development of the marine
layer is the passing upper low well to the north in OR and a 
trailing vort max/shortwave trough passing over region. Lastest 
guidance continues to advertise some expansion of the marine layer
through sunrise, but it never completely fills in the "standard" 
marine layer footprint. Morning low clouds will give way to 
afternoon sunshine, even the coastal locations. The coastal 
clearing today will be enhanced by the increasing northerly 
gradients and stronger winds. SFO-ACV will ramp up to over 5 mb, 
which is decent. Winds will be strongest over the coastal waters 
this afternoon and immediate coastline with gusts of 25-45 mph 
possible. Despite some sunshine temperatures will be close to or 
below normal for mid May with highs in the 60s to lower 70s 
coast/bays and 70s to mid 80s inland. It will be the coldest day 
of the next seven.


For tonight, not expecting a ton of marine stratus due to
lingering stronger northerly flow and a departing upper level
trough. 


&&

.LONG TERM...
Issued at 1204 AM PDT Wed May 13 2026
(Thursday through Tuesday)

By Thursday zonal flow develops over the region as high pressure
begins to build, but is tampered by a trough near the Gulf of AK.
The semi-zonal flow will continue through Friday. As such, a 
gradual warming and drying trend will develop. A blip in the
longwave pattern with a sagging upper level trough over CA on
Saturday will drop temperatures back to near or below seasonal
averages. The sagging trough deepens and develops a low that 
sweeps into the Great Basin. Why is this important for our area? 
Pattern recognition points to bursts of offshore flow over the 
higher terrain each night into morning hours beginning Sunday 
into next week. This will lead to marginal humidity recovery at 
night. Not a big fire concern at this point, but something we'll 
need to monitor over the next few days. ERC charts are catching on
with a trend line back toward daily maxes.

More uncertainty for next week is around max temps Mon/Tue. While
the longwave pattern shows troughing to the east and a ridge over
the EPac it doesn't scream heat. The NBM is showing some rather 
warm temps with interior 90s again. Call it recency bias, but 850 
mb not 20C+ gives me pause on max temps from the NBM. Other ens 
guidance is on the colder side and did verify better during our 
most recent warm spell. That being said, we'll need to watch this 
as well and trend temps down if needed. Stay tuned...


&&

.AVIATION...
(06Z TAFS)
Issued at 1107 PM PDT Tue May 12 2026

Breezy to gusty onshore winds will persist through a majority the
TAF period for sites along the coast. Winds are reducing into the
night, but are expected increase again late morning into the 
afternoon on Wednesday. MVFR cigs continue to develop and 
persisting through late morning Wednesday. The timing and coverage
of IFR/LIFR cigs is low confidence, and if reached may not 
persist for long. 

Vicinity of SFO...MVFR cigs are expected persist through late 
morning Wednesday. Gusty onshore winds extending through much the
TAF period, peaking around 30 kts Wednesday afternoon, but winds
ease Wednesday night.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...MVFR cigs are expected to persist
through the late night, becoming IFR after and continuing through
mid-morning Wednesday. KSNS is expected to clear out Noon with 
some partial clearing possible at KMRY by early afternoon.

&&

.MARINE...
(Tonight through next Sunday)
Issued at 443 PM PDT Tue May 12 2026

Hazardous marine conditions develop midweek and will continue into
next week. Winds increase through the remainder of the week with
strong to near gale force winds and occasional gale force gusts
Wednesday and Thursday. Wind driven seas will build to between 10
to  12 feet Wednesday and Thursday. Surface high pressure will
then  strengthen over the eastern Pacific Friday into next week.
This will  result in a strong coastal jet, widespread gale force
to potentially  severe gale winds, and very high, wind driven seas
between 12 to 17  feet expected.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 AM this morning to 9 PM PDT this 
     evening for Mry Bay.

     Small Craft Advisory until 3 PM PDT Thursday for Pt Arena to Pt 
     Reyes 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

     Small Craft Advisory from 9 AM this morning to 3 PM PDT Thursday 
     for Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-
     60 NM-Pt Arena to Pt Reyes 10-60 NM.

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

&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...Murdock
MARINE...JM

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Prepared by Boulder-Creek.com Weather at: Wed May 13 02:30:03 PDT 2026