FXUS66 KMTR 220848
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
148 AM PDT Wed Jul 22 2026
...New SHORT TERM, LONG TERM...
.KEY MESSAGES...
Updated at 1219 AM PDT Wed Jul 22 2026
- Breezy onshore winds return for the second half of the week
- Temperatures will hover around normal through the week
&&
.SHORT TERM...
Issued at 148 AM PDT Wed Jul 22 2026
(Today and tonight)
Low clouds and the leading edge of cooler air on southwesterly
winds with the eastern side of the northward moving remnant low
(once part of tropical storm Elida) rapidly moved to and filled in
along the coast Tuesday afternoon and evening. The remnant low is
still enveloped by a tropical air mass, but it also has had time
to draw in cooler air into the circulation from the northwest.
This is the air that'll cool our temperatures today, but it'll
also feel muggy and damp today. There may even be a few patches of
light drizzle/light rain in the newly arriving moisture rich and
cooler air mass combination.
Since about 8 pm to 10 pm Tuesday, an increase in surface dewpoint
temperatures (higher water vapor) has spread across about the entire
forecast area. Dewpoint temperatures in the 50s and 60s are now
widespread.
An area of increasing larger scale subsidence and a clearing sky
coincided with maximum diurnal surface heating on Tuesday, boosting
daytime highs well above normal including breaking several record
high temperatures in our forecast area for July 21st. However,
other long term stations such as Santa Rosa, San Francisco, Napa,
Kentfield, San Jose and Livermore with a period of record back
including July 1917 were in the middle of a several day heat wave
this time in 1917; none of these stations reached record highs on
Tuesday.
Daytime highs today will be noticeably cooler even far inland:
60s/70s coastside to the 70s/80 bayside and 80s/90s far inland.
Lows in the 50s to lower 60s tonight.
&&
.LONG TERM...
Issued at 148 AM PDT Wed Jul 22 2026
(Thursday through Tuesday)
More typically drier (gradually less humid) summer weather
develops Thursday onward to the weekend, along with onshore
breezes, night and morning low clouds and fog and possibly
patchy drizzle. High pressure may compress the marine layer over
the weekend bringing a slight warming trend to inland areas.
The latest ECMWF and GFS show dry conditions in the 700-500 mb
layer, mostly if not entirely dominated by mid-latitude winds
over our forecast area for the next 10 days. Any daytime heating
potential instability will be capped by thermal and height ridging
at least out through 84 hours according to the 00z NAM model.
&&
.AVIATION...
(06Z TAFS)
Issued at 959 PM PDT Tue Jul 21 2026
After a hot and clear day with widespread VFR, marine layer stratus
appears to be returning with a vengeance. Stratus associated with an
offshore surface low has begun spilling over the coastal ranges, and
pushing through the gaps and valleys of the Bay Area, Monterey Bay
and the Salinas Valley. Expect MVFR ceilings with onset, and low
confidence of timing or extent of IFR/LIFR through the overnight
hours.
Vicinity of SFO...Stratus making a steady push through the Golden Gate and
spilling over the San Francisco peninsula coastal range. The
progression is faster than previous guidance indicated but still
don't expect MVFR/IFR ceilings until after midnight. Expect breezy
onshore winds at times overnight increasing by Wednesday afternoon.
MVFR/IFR ceilings are expected to lift by early afternoon.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Stratus accelerated through Monterey Bay into the
Salinas Valley after sunset and has already settled in with a MVFR
ceiling at KSNS. The northwest onshore flow currently at KMRY is
holding off the easterly push of stratus for the moment, however the
stratus should fill in shortly over the terminal. Expect clearing
to VFR by early afternoon, until sunset when stratus ceilings
return.
&&
.MARINE...
(Tonight through next Monday)
Issued at 959 PM PDT Tue Jul 21 2026
Gusty southerly winds over the inner coastal waters and across
the San Francisco Bay to the Delta will continue tonight.
Otherwise west-northwest breezes tonight will gradually increase
through the morning into Wednesday afternoon become northwest
with fresh to moderate breezes continuing into the weekend.
Moderate southwesterly swell from tropical cyclone activity in the
Eastern Pacific will bring mixed seas with potentially hazardous
conditions through the weekend.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Wednesday for SF Bay N of
Bay Bridge.
Small Craft Advisory from 9 PM Wednesday to 9 PM PDT Thursday
for Pt Pinos to Pt Piedras Blancas 0-10 nm.
&&
$$
SHORT TERM...Canepa
LONG TERM....Canepa
AVIATION...JM
MARINE...JM
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Prepared by Boulder-Creek.com Weather at: Wed Jul 22 02:30:03 PDT 2026
From the National Weather Service
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