FXUS66 KMTR 221126
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
426 AM PDT Wed Jul 22 2026
...New AVIATION, MARINE...
.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...
(12Z TAFS)
Issued at 409 AM PDT Wed Jul 22 2026
The marine layer quickly reorganized last night, and is now around
1800 feet deep according to the 12Z weather balloon. The stratus
pattern is a little non-standard, however. Winds are out of the
south to southwest, meaning the coastal stratus is interacting
with the mountains differently than the standard NW regime. Winds
will gradually shift back to west and NW through the day as the
clouds retreat back to the coast.
Vicinity of SFO...The southerly winds are a big help to SFO this
morning. Stratus is banked up along the taller Santa Cruz
mountains. With a marine layer depth of 1,800 feet, the clouds are
unable to cross the ridge and spill over to the terminal. There is
a separate patch of stratus forming over the East Bay hills that
may expand to reach the terminal, but it's not totally clear if
the terminal will develop a ceiling or not. The best window is
between 12-18Z. If the winds change back to NW, the probability
of a ceiling goes way up.
SFO Bridge Approach...More likely to stay clear than SFO this
morning.
Monterey Bay Terminals...MRY and SNS are both socked in this
morning. The cloud base has actually started to rise thanks to
moderate winds. If those winds can hold on, it's unlikely IFR
conditions will return this morning. MRY will probably only get a
few hours of clearing this afternoon.
&&
.MARINE...
(Today through Monday)
Issued at 409 AM PDT Wed Jul 22 2026
A moderate southerly wind will gradually shift to NW through
Wednesday afternoon. Winds will increase to a fresh NW breeze
Thursday-Friday, with similar conditions continuing into next
week. Significant wave heights will remain moderate this week
before long period southerly swell from Hurricane Fausto reaches
the coastal waters this weekend.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 AM to 9 PM PDT Thursday for Mry Bay.
Small Craft Advisory from 3 PM Thursday to 3 AM PDT Friday for
Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm.
Small Craft Advisory from 9 AM Thursday to 3 AM PDT Friday for
Pigeon Pt to Pt Pinos 0-10 nm.
Small Craft Advisory from 9 PM this evening to 3 AM PDT Friday
for Pt Pinos to Pt Piedras Blancas 0-10 nm.
&&
$$
SHORT TERM...Canepa
LONG TERM....Canepa
AVIATION...Flynn
MARINE...Flynn
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Prepared by Boulder-Creek.com Weather at: Wed Jul 22 08:30:03 PDT 2026
From the National Weather Service
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