Technical NOAA Weather Discussion

FXUS66 KMTR 221938
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1238 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 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...
(18Z TAFS)
Issued at 1107 AM PDT Tue Sep 22 2026

MVFR to IFR ceilings associated with the marine layer will gradually 
scatter out in the next couple of hours, resulting in widespread VFR 
conditions at most terminals. Low confidence on whether HAF will see 
the sun as there may be a brief period of scattered clouds before 
becoming BKN again. The usual diurnal onshore wind pattern prevails 
through the afternoon with a light south to southwest flow overnight 
across our region. The marine layer will compress overnight. Exactly 
how much is uncertain. Moderate confidence for STS, LVK, SJC, and 
SFO to remain VFR through the TAF cycle with advertised SCT decks 
early Wednesday morning. There is a 60-70% chance for APC and OAK to 
develop BKN ceilings given their exposed locations, though it may be 
intermittent depending on the marine layer depth tonight.

Vicinity of SFO...VFR prevails this afternoon with low to medium 
confidence on the return of MVFR ceilings tonight. Should ceilings 
develop, they will likely roll in around the time of the SCT decks 
as advertised. OAK has a higher probability of developing MVFR 
ceilings early Wednesday morning compared to SFO. Westerly winds 
increase to moderate this afternoon and ease to a light 
southwesterly flow Wednesday morning before increasing again.

SFO Bridge Approach...Current satellite imagery shows a final push 
of stratus across the bridge, but should become VFR in the next hour 
or so. Patchy cloud cover is possible over the eastern side of the 
bridge tonight. Otherwise, similar to SFO.

Monterey Bay Terminals...Borderline MVFR-IFR ceilings linger through 
the next couple of hours with a brief period of VFR conditions. 
Medium to high confidence for an early onset of IFR ceilings around 
4-7 PM PDT impacting MRY first and then SNS. Low confidence on 
whether ceilings will drop to LIFR territory early Wednesday 
morning. For now, the TAF advertises borderline IFR-LIFR with slight 
impacts to visibility due to mist and/or drizzle. Onshore winds 
increase to 7-10 kt this afternoon and gradually become light 
southerly breezes overnight. 

&&

.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 until 9 PM PDT this evening for Pigeon Pt 
     to Pt Pinos 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.

     Small Craft Advisory until 5 AM PDT Wednesday for Pigeon Pt to 
     Pt Pinos 10-60 NM.

&&

$$

SHORT TERM...RGass
LONG TERM....RGass
AVIATION...Navarrete
MARINE...Navarrete

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Prepared by Boulder-Creek.com Weather at: Tue Sep 22 14:30:03 PDT 2026
From the National Weather Service