FXUS66 KMTR 160452
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
952 PM PDT Thu Oct 15 2026

...New AVIATION...

.KEY MESSAGES...
Updated at 1149 PM PDT Wed Oct 14 2026

 - Above normal temperatures continue into the weekend before a
   cooling trend begins Sunday into next week

 - Near critical fire weather conditions due to moderate flow and
   very dry conditions across the higher elevations Thursday and
   Friday

 - Potential for light rain and breezy onshore winds early to mid
   next week

&&

.UPDATE...
Issued at 858 PM PDT Thu Oct 15 2026

The Red Flag Warning for the North Bay Interior Mountains goes 
into effect at 10 PM this evening and will remain in effect
through 11 AM Friday. Offshore winds are picking up across the 
highest peaks within the North Bay Interior Mountains with gusts 
reaching 30 to 50 mph. The strongest gusts will be confined to 
these highest elevations but moderate offshore winds are expected
to mix into the rest of the zone by late tonight/early Friday.
Humidity values are expected to drop as offshore winds strengthen
with most locations seeing overnight humidity values between 15
to 25%. If a fire is able to develop it has the potential for
rapid spreed given how critically dry conditions are. Near
critical fire weather conditions continue across the higher
elevations for the rest of the Bay Area through Friday morning.

&&

.SHORT TERM...
Issued at 132 PM PDT Thu Oct 15 2026
(This evening through Friday night)

Another warm and sunny day across our area with offshore flow 
providing above normal temperatures and abundant sunshine. With an 
upper level ridge over NorCal and upper level low over SoCal, we're 
seeing a common setup for a relatively weak Diablo wind event 
through the North Bay interior mountains, which has resulted in a 
Red Flag Warning issued for 10p tonight through 11am Friday for that 
area. The highest peaks around Mt St Helena have already seen gusts 
between 50-60 mph and we expect that to continue until winds at 
lower altitude begin to increase later tonight through late 
morning Friday. It hasn't rained in that part of the North Bay 
since September 4th, so conditions and fuels are very dry (see the
Long Term discussion below for how that may change next week). 
Elevated fire weather concerns extend beyond the Red Flag Warning 
so we continue to message to abstain from any activities that 
could ignite a wildfire. The offshore flow continues to work 
against marine layer development with some of our coastal 
locations like Half Moon Bay and Monterey already in the low 80s 
and representing some of our highest temperatures of the day so 
far.

The offshore flow will continue tonight providing clear skies 
area wide. Thermal belting above 1000ft over much of our area will
result in poor RH recovery and overnight lows well above normal, 
providing little relief from the heat until at Saturday night.

&&

.LONG TERM...
Issued at 132 PM PDT Thu Oct 15 2026
(Saturday through next Wednesday)

We expect the Red Flag warning over the North Bay interior 
mountains to expire at 11am Friday with easing winds as the 
mitigating factor, temperatures will remain warm with very dry 
conditions and fuels persisting through Saturday until a notable 
pattern change sets in on Sunday.

An upper level trough to our north will approach the coast over 
the weekend bringing a return of onshore flow, a subsequent cold 
front and notably cooler temperature and multiple days through 
the middle of next week with scattered light rain chances. We're 
not expecting any one location to see more than a 0.25", and most 
locations that see some rain will get less than a 0.10" but 
confidence is increasing that most of our area will see at least a
little bit of rainfall, with exact timing still too far out to 
speak of with any confidence.

&&

.AVIATION...
(06Z TAFS)
Issued at 950 PM PDT Thu Oct 15 2026

Not much change from previous TAF package...VFR through the 
forecast period due to offshore flow and dry air. Biggest 
challenge aviation wise will be dialing the winds. At points winds
will be relatively light and variable. Offshore flow will 
strongest over the N and E Bays. Didn't include in the TAF for 
STS/OAK, but marginal (20-30% chc) of LLWS. LLWS most likely from 
08-15Z.  

One new item for the 06Z will be monitoring winds for KHAF early
tomorrow. In these offshore flow set ups winds can sometimes 
align for the E to NE and increase as they surface toward the 
ocean.

Vicinity of SFO...VFR. Offshore push for the Friday AM rush.
Onshore heading into the Friday afternoon rush.

SFO Bridge Approach...VFR.

Monterey Bay Terminals...VFR.

&&

.MARINE...
(Tonight through next Wednesday)
Issued at 934 PM PDT Thu Oct 15 2026

High pressure to the north will maintain gentle to moderate
northerly breezes over the coastal waters through Friday. A storm
passing well to the north will usher in moderate to fresh
northerly breezes this weekend. The increasing winds will bring a
fresh swell and steeper wind waves.

&&

.FIRE WEATHER...
Issued at 132 PM PDT Thu Oct 15 2026

A Red Flag Warning was issued for the North Bay Interior 
Mountains that goes into effect at 10PM tonight and runs through 
11AM Friday morning. This is due to moderate offshore winds very 
dry with very poor overnight humidity recoveries only reaching 15 
to 25 percent. Rapid fire spread is possible given the 
combination of gusty northerly winds and very dry overnight 
conditions.

Elsewhere in the Bay Area, elevated to near critical fire weather
conditions continue for the higher elevations late tonight 
through Friday morning. Dry conditions, poor overnight RH 
recovery, combined with the breezy winds, warmer weather, and 
available fuels leads to the elevated to near critical fire 
weather conditions. 

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Red Flag Warning until 11 AM PDT Friday for CAZ504.

PZ...None.
&&

$$

SHORT TERM...JM
LONG TERM....JM
AVIATION...MM
MARINE...MM

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Prepared by Boulder-Creek.com Weather at: Thu Oct 15 22:30:04 PDT 2026