Technical NOAA Weather Discussion

FXUS66 KMTR 221606
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
906 AM PDT Tue Sep 22 2026

...New UPDATE, MARINE...

.KEY MESSAGES...
Updated at 1201 AM PDT Tue Sep 22 2026

 - Warming trend begins today through Thursday

 - Cooler conditions Friday into the weekend

&&

.UPDATE...
Issued at 904 AM PDT Tue Sep 22 2026

There was coastal drizzle reported at several locations this 
morning, but nothing more than a few hundredths of an inch. Stratus 
pushed well inland into most interior valleys early this morning and 
is forecast to retreat to the immediate coast by late morning/early 
afternoon. This will give way to mostly sunny conditions inland this 
afternoon with temperatures warming into the 60s near the coast, 
upper 60s to low 70s around the bayshore, and mid 70s to mid 80s 
across the interior. Coastal areas will be some 5-10 degrees below 
seasonal averages with the interior holding near average. A warming 
trend remains on tap for Wednesday and Thursday, yet no significant 
heat anticipated with this brief warming trend. 

RGass

&&

.SHORT TERM...
Issued at 1201 AM PDT Tue Sep 22 2026
(Today and tonight)

Extensive stratus has flowed into the North Bay valleys, Monterey 
Bay region, Salinas Valley, Hollister area, and the East Bay west of 
the Berkeley Hills. Across the rest of the SF Bay Area, patches of 
stratus have developed near Livermore and north of San Jose, with 
further expansion expected through the pre-dawn hours. The cloud 
deck retreats back to the immediate coast late this morning into the 
early afternoon, but by the time it develops again tonight, the 
marine layer will be compressed, leading to uncertainty over just 
how far inland the clouds will go. 

The cut-off low that gave us the last couple days of cooler 
temperatures is moving across the state with the center crawling 
through the Mojave Desert into the Great Basin. This allows for more 
zonal flow to come into the state and a warming trend to begin 
today, with high temperatures in the upper 70s to the middle 80s 
across the inland valleys, into the upper 80s in the far interior 
regions of the North Bay and southern Monterey County, the middle 
60s to the middle 70s close to the Bays, and the lower to middle 60s 
along the immediate coast. A breezy onshore wind will develop in the 
afternoon and evening hours, with the strongest gusts of 20 to 30 
miles per hour along the coast, through favored gaps and passes, and 
within the northern Salinas Valley.

As a quick side note, today will mark the autumnal equinox and the 
start of astronomical fall. At 505 PM Pacific time, the sun's 
apparent path on the Earth crosses the equator, giving us 12 hours 
each of sunlight and nighttime.

&&

.LONG TERM...
Issued at 1201 AM PDT Tue Sep 22 2026
(Wednesday through Monday)

Slight ridging will develop over California over the next couple of 
days, and while the ridge axis quickly moves into the Intermountain 
West, the ridge influence will allow for further warming Wednesday 
and Thursday. High temperatures warm into the middle 80s to the 
middle 90s in the inland valleys, the middle 70s to the middle 80s 
close to the Bays, and the middle 60s to the lower 70s along the 
Pacific Coast. Pockets of Moderate HeatRisk are scattered across the 
interior regions, particularly near San Jose, the interior East Bay, 
and the Santa Lucia range. These pockets are not expansive enough to 
merit a Heat Advisory. 

By Friday, a developing trough in the eastern Pacific comes into the 
West Coast, and a cooling trend will cause temperatures to dip near 
and below seasonal averages. Weekend highs range from the middle 70s 
to the middle 80s in the inland valleys and the middle 60s to the 
middle 70s close to the Bays. Temperatures will recover early next 
week as the trough flattens and ensemble model cluster analysis 
hints at a ridge developing somewhere within the western United 
States, although the exact impacts are not certain at this point.

&&

.AVIATION...
(12Z TAFS)
Issued at 427 AM PDT Tue Sep 22 2026

Solid marine layer push overnight leading to mostly MVFR to IFR
conditions. Seeing some compression on the marine layer leading 
to some patchy fog and dz/ra being reported. Expect 
clearing/rolling back to the coast mid to late morning most areas.
HAF and MRY will hold onto CIGS for most of the day. Tonight, N-S
gradient increases so less conf for stratus N and E Bay. Overall 
conf is moderate. 

Vicinity of SFO...Much more optimistic for the TAF as SE flow
caused rapid drying/clearing earlier in the night. Still watching
a bank of clouds due E of SFO inching W. Carrying a tempo for now,
but conf is low on actual impacts to terminal.  

SFO Bridge Approach...Similar to SFO. CIGs far E fringe of
approach.

Monterey Bay Terminals...IFR with low cigs, br, and dz/ra through
18z-ish . A few hours of VFR this afternoon, but CIGs and 
MVFR/IFR return early tonight.

&&

.MARINE...
(Today through Sunday)
Issued at 904 AM PDT Tue Sep 22 2026

Fresh northwest breezes with strong gusts gradually diminish 
across the southern coastal waters by Wednesday morning. Wind 
driven rough seas abate to moderate for a brief period Wednesday 
night into Thursday with widespread moderate northwest winds. By 
Friday, winds increase with building rough seas.

&&

.FIRE WEATHER...
Issued at 434 AM PDT Tue Sep 22 2026

Solid marine layer coverage along the coast and Salinas Valley
overnight. Sounding and profilers put the depth of the marine
layer around the 2,000-2,500 foot range. Definitely some
compression on the marine layer leading to drizzlefest around the
area. Seeing some reduced vsby too, which may lead to patchy fog
early this morning for crews departing ICP for Timber/Plaskett.
Above the marine layer moderate to excellent humidity recovery 
for the most part with the driest conditions above 3,000 feet. 
Otherwise, still valid for a warming and drying trend kicking off 
Tuesday with temperatures up to 10 degrees above normal and areas 
of moderate HeatRisk Wednesday and Thursday. The marine layer will
compress below 1,000 feet during this warm-up with nocturnal 
drying expected above it.

MM

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 5 AM PDT Wednesday for Pt Arena to Pt 
     Reyes 0-10 nm.

     Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this 
     evening for Pigeon Pt to Pt Pinos 0-10 nm.

     Small Craft Advisory from 3 PM this afternoon to 3 AM PDT 
     Wednesday for Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory until 3 AM PDT Thursday for Pt Arena to Pt 
     Reyes 10-60 NM.

     Small Craft Advisory from 3 PM this afternoon to 5 AM PDT 
     Wednesday for Pigeon Pt to Pt Pinos 10-60 NM.

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...MM
MARINE...Navarrete

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Prepared by Boulder-Creek.com Weather at: Tue Sep 22 10:30:03 PDT 2026
From the National Weather Service