FXUS66 KMTR 041537
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
837 AM PDT Sun Oct 4 2026
...New UPDATE, 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
&&
.UPDATE...
Issued at 833 AM PDT Sun Oct 4 2026
Satellite imagery has shown high clouds streaming across the SF Bay
Area with reported temperatures in the North Bay currently
falling below the current forecast. If this continues through the
morning into the afternoon the high temperatures across the North
Bay may need to be adjusted downwards. Will continue to monitor
the evolution of the cloud cover throughout the day. Otherwise
forecast remains on track.
DialH
&&
.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 nudge 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...
(12Z TAFS)
Issued at 415 AM PDT Sun Oct 4 2026
Strong high pressure aloft is compressing the marine layer to 500
feet or less. A patch or two of fog /LIFR/ are possible this morning
otherwise VFR is forecast during the 12z TAFs.
Vicinity of SFO...VFR. Mainly west wind 5 to 15 knots.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR. East to southeast cool air drainage
winds 5 to 10 knots in the morning, becoming onshore 5 to 10 knots
in the afternoon. East to southeast winds 5 to 10 knots late tonight
and Monday morning.
&&
.MARINE...
(Today through Friday)
Issued at 833 AM PDT Sun Oct 4 2026
Northwesterly breezes will remain gentle to moderate into
midweek, allowing for slight to moderate wave heights to persist.
&&
.FIRE WEATHER...
Issued at 405 AM PDT Sun Oct 4 2026
Hot and dry conditions will continue 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. If working in the
thermal belts, Moderate to Extreme HeatRisk is forecast this week,
with temperature and HeatRisk trends improving late week. A
pattern change is expected late in the week or over the weekend.
Cooler weather and the potential for improved RH recovery is
forecast or 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...Canepa
MARINE...RGass
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Prepared by Boulder-Creek.com Weather at: Sun Oct 4 10:30:03 PDT 2026
From the National Weather Service
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