Technical NOAA Weather Discussion

FXUS66 KMTR 230602
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1102 PM PDT Tue Sep 22 2026

...New SHORT TERM, LONG TERM...

.KEY MESSAGES...
Updated at 1232 PM PDT Tue Sep 22 2026

 - Warming trend continues through Thursday

 - Cooler conditions Friday into the weekend

&&

.SHORT TERM...
Issued at 1103 PM PDT Tue Sep 22 2026 (Tonight through Thursday)

Marine layer between 1500-2000 feet deep as of Tuesday evening.
Low clouds cover areas from Point Reyes southward to Big Sur with
a decent push of stratus in SF Bay and the Monterey Bay region
including Salinas valley. There is an increasing northerly
gradient now to about 5 mb from ACV-SFO that is eroding the 
stratus from north to south for the North Bay. This is occurring 
as high pressure is trying to nose into the region from the 
southwest. 850 mb temps warming to around 20-21 celsius with hot 
inland temps for the interior Central Coast (90s) with mainly 
upper 80s to around 90 for the interior North/South/East Bays on 
Weds afternoon. With persistent onshore winds not really a late 
September setup where we would expect warm/hot temps at the coast.
Looking at the European extreme forecast index we see no areas of
interest suggesting this is just a typical warm late Sept day on 
tap. Models hold onto the warm inland temps for one more day 
through Thursday. However by Thursday afternoon a storm well to 
our north will induce a strong onshore/westerly push, ushering in 
a moderate to strong afternoon/evening seabreeze on Thursday that 
will signal relief for the Bay Area while the interior Central 
Coast remains warm/hot through Thursday evening.

&&

.LONG TERM...
Issued at 1103 PM PDT Tue Sep 22 2026 (Thursday night through 
next Tuesday)

A fairly well defined early autumn dry cold front passage will push
through the region Thursday night into Friday morning. No precip 
is forecast for the Bay Area as it remains confined to areas north
of Cape Mendocino. However, enough cooling and mixing aloft to 
essentially erode or mix out the marine layer quickly by early Friday
morning. Temps still remain seasonably warm/mild Friday but the 
cooling trend will have begun. Weather this weekend looks nice for
the last weekend of September. Certainly no hot weather with 
inland temps mainly 70s to lower 80s Saturday/Sunday with enough 
cold air aloft and mixing to keep skies sunny with perhaps only 
some patchy morning low clouds near the coast and bays. 

Early look at next week shows no signal for precip or abnormally
hot weather and no fall offshore wind events. Pattern looks pretty
zonal suggesting temps running near seasonal norms. 

&&

.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.

&&

.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...RW
LONG TERM....RW
AVIATION...JM
MARINE...JM

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, X, and YouTube at:
www.facebook.com/nwsbayarea
x.com/nwsbayarea
www.youtube.com/nwsbayarea


  
Prepared by Boulder-Creek.com Weather at: Wed Sep 23 04:30:04 PDT 2026
From the National Weather Service