FXUS66 KMTR 130033
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
533 PM PDT Tue May 12 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 1200 PM PDT Tue May 12 2026
- Cooling trend continues today and Wednesday
- Elevated fire weather risk for far interior San Benito and
Monterey counties this afternoon and evening
- Warming and drying trend resumes Thursday through the weekend
&&
.SHORT TERM...
Issued at 1200 PM PDT Tue May 12 2026
(This evening through Wednesday)
The satellite imagery shows stratus coverage across the coastal
regions and some lingering into the valleys of the Bay Area as a
thin layer of high clouds persists over the region, with gradual
clearing across the inland and Bayshore regions into the afternoon
while the coast remains socked in. Stratus coverage should rebuild
this evening and overnight but should not come as far into the
southern Salinas Valley or the North Bay valleys as we saw this
morning.
The large scale weather pattern features a departing ridge moving
into the northern and central Rockies while a trough centered on an
upper level low around 500 miles to the west of the Oregon Coast
moves in, resulting in a gradual cooling trend today into Wednesday
and an expansion of the marine layer. The latest readings from the
Bodega Bay profiler suggest a marine layer around 1500-2000 feet
thick, remaining rather consistent through the next couple of days
as the trough passes through the region. High temperatures today
will range from the upper 70s to the lower 80s in the inland
valleys, the upper 80s to lower 90s in southern Monterey and San
Benito Counties, the middle 60s to the middle 70s in the bayshore
regions, and the upper 50s to lower 60s along the Pacific coast.
Highs might be a few degrees cooler where the stratus is slower to
dissipate than the forecast or does not clear out this afternoon.
Low temperatures on Wednesday morning range from the upper 40s to
the middle 50s across the lower elevations, while Wednesday's highs
will range from the lower 70s to the lower 80s for the inland
valleys.
As the trough moves through, the increasing pressure gradients will
result in breezy and gusty winds starting this afternoon through
Wednesday, with the gusts reaching 20 to 30 mph across the coastal
and higher elevation regions and the northern Salinas Valley.
Isolated favored regions, namely the Mayacama range and the Altamont
Pass, may reach gusts of 40 to 45 mph this evening and overnight.
Elevated fire weather risks will set up starting this afternoon
across a narrow strip of the far interior San Benito and Monterey
counties adjacent to the Central Valley. A particularly concerning
combination of gusty winds, hot temperatures, low daytime
humidities, and poor overnight humidity recoveries across this
region will result in a period of elevated fire weather concerns
across this strip through the evening hours. Any fires that start in
the drier grasses across this region may take hold and spread rather
quickly. Our neighbors in Hanford have issued a Red Flag Warning for
the adjacent zones across the western edge of Fresno County, but in
our area of responsibility. the fire weather concerns are not
widespread enough to warrant any products.
&&
.LONG TERM...
Issued at 1200 PM PDT Tue May 12 2026
(Wednesday night through next Monday)
As the trough moves out, warmer and drier weather will return to the
region with highs on Thursday and Friday in the 80s to the lower 90s
in the interior valleys, the middle 70s to lower 80s across the
Bays, and the lower to middle 60s in the Pacific coast. A second
trough coming down from the Gulf of Alaska will interrupt the
warming trend this weekend, with inland highs dipping in to the
lower 70s to lower 80s on Saturday before bouncing back to the upper
70s to middle 80s for Sunday.
Uncertainty in the forecast starts to increase in the early part of
next week as the ensemble models struggle to diagnose the
interaction between an upper level ridge and trough over the western
United States. Model ensemble means from the American GEFS, European
ECMWF, and Canadian GEPS models suggest a ridge over the eastern
Pacific and a trough over the Rockies should develop by Monday
morning, although with significant differences in the strength of
both features. However, a peek into the model ensemble clusters
reveals a significant minority of the ensemble members (around 30-
40%) show an alternate scenario where more zonal flow or troughing
develops over the West Coast, nudging the forecast towards cooler
temperatures. Past the 7-day outlook, CPC outlooks into the later
part of May show a slight lean towards temperatures above seasonal
averages, and precipitation totals near or above seasonal
averages.
&&
.AVIATION...
(00Z TAFS)
Issued at 443 PM PDT Tue May 12 2026
Gusty onshore winds will persist through a majority the TAF
period for sites in proximity to the ocean/bay. Winds are expected
to ease slightly after midnight for Bay Area terminals, but then
increase again late morning into the afternoon on Wednesday for
the remaining sites due to a dry cold front moving east across the
northern portion of our forecast area. Guidance is confident on
MVFR cigs developing after midnight 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 to develop by midnight
and persist through late morning Wednesday and gusty onshore
winds extending through the TAF period. An Airport Weather Warning
is in place until 11pm PDT tonight for wind gusts reaching 40 MPH
at times.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...MVFR cigs are expected to persist tonight
through Wednesday morning at both KMRY and KSNS. There's more
confidence in KMRY becoming IFR/LIFR after midnight 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 to 9 PM PDT Wednesday for Mry Bay.
Small Craft Advisory until 9 AM PDT Thursday for Pt Arena to Pt
Reyes 0-10 nm.
Small Craft Advisory until 3 AM PDT Thursday for Pt Reyes to
Pigeon Pt 0-10 nm.
Small Craft Advisory from 9 AM Wednesday to 3 AM PDT Thursday
for Pigeon Pt to Pt Pinos 0-10 nm.
Small Craft Advisory from 3 AM Wednesday to 9 AM PDT Thursday
for Pt Pinos to Pt Piedras Blancas 0-10 nm.
Small Craft Advisory from 9 AM Wednesday to 9 AM PDT Thursday
for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-
60 NM.
&&
$$
SHORT TERM...DialH
LONG TERM....DialH
AVIATION...JM
MARINE...Kennedy
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Prepared by Boulder-Creek.com Weather at: Tue May 12 18:30:03 PDT 2026
From the National Weather Service
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