FXUS66 KMTR 230428
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
928 PM PDT Tue Sep 22 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 1232 PM PDT Tue Sep 22 2026
- Warming trend continues through Thursday
- Cooler conditions Friday into the weekend
&&
.UPDATE...
Issued at 834 PM PDT Tue Sep 22 2026
Marine layer around 1500-2000 feet based on 00z sounding and
local observations. SFO to Sac gradient is 2.6 mb and stratus
covering West Marin, all of the City and up into the Berkeley
hills early this evening. Ridging to our southwest is trying to
nose in and compress the marine layer overnight into Weds but
seems to be having trouble with active PacNW trough and incoming
surface low that will take aim on the Oregon coast by Thursday
with some rain up there. Meanwhile well to our south Hurricane
Polo is now a dangerous category 5 with Tropical Storm Odalys well
to its west...after a brief lull the East Pac is active again. It
would seem we are fortunate the PacNW trough remains fairly
strong for so early in the autumn and seemingly keeping any of the
remnant tropical activity well to our south. Latest cluster
analysis shows fairly strong trough over the West Coast this
weekend that will keep Bay Area temps below normal this weekend
behind a dry cold frontal passage on Friday that will keep fall
like temps in the 60s and 70s this weekend. Long range cluster
trends for next week show more troughing than ridging with no real
hint of hot Sept weather. This long wave pattern would continue
to shunt any East Pac moisture well to our south and east.
&&
.SHORT TERM...
Issued at 1232 PM PDT Tue Sep 22 2026
(This evening through Wednesday night)
An upper level trough is moving across Nevada this afternoon and
will continue to shift into the Great Basin on Wednesday. As such,
temperatures this afternoon are forecast to warm into the 60s near
the coast, upper 60s to low 70s around the bayshore, and mid 70s to
mid 80s across the interior with mostly sunny sky conditions across
the interior. Breezy onshore flow will develop in the afternoon and
evening hours with gusts of 20 to 30 mph near the coast, in the
favored gaps and passes, and down the Salinas Valley.
As the marine layer gradually compresses to around 1,500 feet
tonight, we are expecting less of an inland intrusion of stratus. As
such, temperatures are expected to cool into the 50s for much of the
region overnight. More of a zonal flow is forecast on Wednesday
which will lead to a warming trend. Temperatures Wednesday afternoon
are forecast to reach into the upper 60s to mid 70s near the coast,
upper 70s to mid 80s around the bayshore, and mid 80s to low 90s
across the interior. The warmest interior portions of the Central
Coast look to warm into low-to-upper 90s. This will result in
pockets of moderate HeatRisk across the interior. As a result, drier
conditions are forecast in elevations above the marine influences.
Tomorrow night, look for again less inland extent of stratus and the
warming trend to continue. Overnight temperatures are forecast to be
in the mid 50s near the coast to lower 60s across the interior.
However, the warming air mass aloft will result in the higher
terrain only cooling into the 70s.
&&
.LONG TERM...
Issued at 1232 PM PDT Tue Sep 22 2026
(Thursday through next Monday)
Thursday looks to be the warmest across the interior with similar
temperatures to Wednesday elsewhere. On Friday, a developing trough
off of the West Coast will return resulting in a cooling trend and
deepening of the marine layer. The coolest conditions are expected
Saturday and Sunday as a reinforcing trough deepens off of the
California coast with temperatures up to 10-15 deg F below
seasonal averages. Temperatures appear to rebound closer to normal
for this time of year early next week as the trough flattens and
the 500 mb height clusters point to a building ridge over the
western United States.
&&
.AVIATION...
(06Z TAFS)
Issued at 926 PM PDT Tue Sep 22 2026
The marine layer is difficult to to pin down tonight. It's
expected to compress somewhat under ridging aloft but is also
showing signs of a farther push inland than expected. North Bay
and interior South Bay continue with VFR conditions with low
confidence in IFR ceilings developing late in the overnight toward
sunrise for the North Bay. Moderate confidence in VFR persisting
through the remainder of the forecast period at KSJC and KLVK.
Vicinity of SFO...MVFR/IFR ceilings settled in earlier than expected
and are expected to now persist through mid/late morning
Wednesday with VFR expected into the evening hours after lifting.
Breezy onshore flow develops Wednesday afternoon, then eases by
midnight.
SFO Bridge Approach...Similar SFO.
Monterey Bay Terminals...More typical diurnal pattern is expected with
VFR conditions expected by late morning, with VFR through the
remainder of Wednesday afternoon and early evening, MVFR/IFR
ceilings return after sunset.
&&
.MARINE...
(Tonight through next Monday)
Issued at 926 PM PDT Tue Sep 22 2026
Moderate to fresh northwest breezes will continue to diminish
overnight into Wednesday with persistent rough northwest seas that
will gradually ease to moderate on Thursday. Friday will see an
increase in northwest winds accompanied by seas building back up
to rough, and continuing into the weekend.
&&
.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 Pigeon Pt to
Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm.
Small Craft Advisory until 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.
&&
$$
SHORT TERM...RGass
LONG TERM....RGass
AVIATION...JM
MARINE...JM
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Prepared by Boulder-Creek.com Weather at: Tue Sep 22 22:30:03 PDT 2026
From the National Weather Service
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