345
FXUS66 KMTR 040901
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
201 AM PDT Sun Oct 4 2026

...New MARINE...

.KEY MESSAGES...
Updated at 1216 AM PDT Sun Oct 4 2026

 - Moderate to major HeatRisk across the Bay Area and Central
   Coast Sunday

 - Moderate to major HeatRisk across the interior Bay Area and
   Central Coast Monday through Thursday

 - Elevated fire weather conditions across the higher terrain
   through Thursday

&&

.SHORT TERM...
Issued at 1216 AM PDT Sun Oct 4 2026
(Today and tonight)

The 00Z sounding observed the second hottest 850 mb temperature for
the date and time at 24.35 degrees Celsius; however, no daily
maximum temperature records were broken. The Heat Advisory has been
extended in area to now include all of the Bay Area and Central
Coast through 10 PM Sunday. Locations along the immediate coast may
have relatively cooler conditions; however, weaker than normal
onshore flow will limit relief even just a couple miles inland.
Temperatures 10 to 20 degrees above normal and weaker than normal
onshore flow will limit overnight relief, resulting in moderate to
major HeatRisk. Across the higher terrain, elevated fire weather
conditions continue from hot and dry conditions with even less
relief, prominent thermal belting, and prolonged burn periods. Fog
is expected to develop around the Monterey Bay tonight with lower
confidence for other locations along the Pacific Coast. Subsidence
aloft will support a compressed and shallow marine layer that will
mix out shortly after sunrise, providing another nudger that even
the coast will got hot.

&&

.LONG TERM...
Issued at 1216 AM PDT Sun Oct 4 2026
(Monday through Saturday)

There will be subtle fluctuations Monday through Wednesday;
nonetheless, upper-level ridging will prevail. The Heat Advisory
will remain in effect through 10 PM Wednesday for most of the
interior Bay Area and Central Coast as temperatures 10 to 20 degrees
above normal bring moderate to major HeatRisk. The Marin Hills,
Northern Monterey Bay, and Northern Salinas Valley (including Carmel
Valley and Hollister Valley) may need to be grouped in as well with
similar conditions and high probabilities for moderate to major
HeatRisk. San Francisco will also remain a contender with 60%+
probability for the eastern half of the city to reach 80 degrees
Monday and Tuesday with probabilities dropping below 60% by
Wednesday except for the far southeastern part of the city. Moderate
HeatRisk will persist into Thursday across the interior with areas
of major HeatRisk across the North Bay Interior Mountains, Interior
East Bay, Santa Cruz Mountains, and Santa Lucia Mountains. Elevated
fire weather conditions will continue through Thursday across the
higher terrain from the hot and dry conditions. Global ensemble
clusters show signs of the upper-level ridge weakening Thursday with
troughing off the West Coast likely (80% chance) by Saturday. As a
result, HeatRisk will drop below hazardous levels Friday with
temperatures moderating to near to slightly below normal by
Saturday. It`s at the tail end and beyond the long term forecast,
but something to watch will be if the aforementioned trough brings
remnant tropical moisture from Hurricane Rachel.

&&

.AVIATION...
(06Z TAFS)
Issued at 932 PM PDT Sat Oct 3 2026

The 00Z weather balloon found no trace of a marine layer at
Oakland. With high pressure, warm temperatures and weak offshore
winds VFR conditions are highly likely at all but the most coastal
terminals through the TAF period. MRY and HAF are the exceptions,
where there is a decent chance for brief LIFR conditions due to
fog around sunrise. Even if that happens, it will clear quickly
with VFR conditions and high clouds expected across the terminals
Sunday.

Vicinity of SFO...Westerly winds are calming down, with a gentle
breeze expected through the night. There is a 90% chance that VFR
conditions persist through the TAF period. W-NW winds will reach
10-15 knots Sunday afternoon as high clouds roll in.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Pretty interesting forecast for MRY.
There is a 9C dew point depression at the moment, but it was 14C
less than an hour ago. With moderate onshore winds, there is
finally some marine influence being felt at the terminal. With
high pressure aloft, clear skies and light winds Sunday morning,
all the ingredients are there for fog in the morning. At the
Monterey buoy, the dew point matches the warm sea surface
temperature (16C) and the air temperature is only slightly warmer
(16.2C). That`s a pretty ideal set-up for fog formation, but it
hasn`t formed in the Bay yet.

&&

.MARINE...
(Today through Friday)
Issued at 201 AM PDT Sun Oct 4 2026

A gentle to moderate NW breeze and moderate wave heights will
prevail for the next several days.

&&

.FIRE WEATHER...
Issued at 111 PM PDT Sat Oct 3 2026

Hot and dry conditions are forecast through Thursday, which will
be accompanied with weak offshore flow. Poor to very poor
overnight recovery is expected for the thermal belts, generally
for elevations above 1000-1500 feet, leading to elevated fire
weather conditions. The marine layer is expected to be confined to
the immediate coast and around 500 feet. A pattern change is
expected late in the week, which should start to bring cooler
weather and the potential for improved RH recovery on Friday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 10 PM PDT this evening for CAZ006-502-505-
     509-528>530.

     Heat Advisory until 10 PM PDT Wednesday for CAZ503-504-506-508-
     510-512>518.

PZ...None.
&&

$$

SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...Flynn
MARINE...Canepa

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