FXUS66 KMTR 021146 CCB
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
442 AM PDT Fri Oct 2 2026
...New AVIATION, MARINE, FIRE WEATHER...
.KEY MESSAGES...
Updated at 1237 AM PDT Fri Oct 2 2026
- Moderate to major HeatRisk across the interior through Thursday
- Elevated fire weather conditions across the higher terrain
through Thursday
- Minor coastal flooding for bayshore locations along the San
Francisco Bay, San Pablo Bay, and Monterey Bay Friday
&&
.SHORT TERM...
Issued at 1237 AM PDT Fri Oct 2 2026
(Today and tonight)
The 00Z sounding observed an 850 mb temperature of 21.75 degrees
Celsius and a 500 mb height of 5900 meters; both of these are above
the 90th percentile of 20.6 degrees Celsius and 5883 meters,
respectively. Upper-level ridging across the Southwest will bring
temperatures 10 to 15 degrees above normal to the interior Friday,
resulting in areas of moderate HeatRisk. Subsidence aloft will
compress the marine layer, keeping it confined to the coast and
supporting fog development. Above the marine layer in the higher
terrain, elevated fire weather conditions continue from hot and dry
conditions with offshore flow overnight. Minor coastal flooding for
bayshore locations along the San Francisco Bay, San Pablo Bay, and
Monterey Bay will occur during high tide Friday afternoon.
&&
.LONG TERM...
Issued at 1237 AM PDT Fri Oct 2 2026
(Saturday through Thursday)
A Heat Advisory is in effect for most of the interior from 11AM
Saturday through 10PM Sunday. This covers the peak of the heat as
upper-level longwave ridging drifts in from the Eastern Pacific
Ocean. A compressed marine layer around 500 feet is currently
forecast during this time; however, if it erodes from offshore flow
or clouds fail to develop, the coast will be hotter than forecast.
Upper-level shortwave troughing will undercut the ridge Sunday into
Monday with the ridge rebounding across the West Coast Tuesday into
Wednesday. No matter how you slice it, it is going to be hot for the
next week with temperatures 15 to 20 degrees above normal and
moderate to major HeatRisk across the interior. A compressed marine
layer, weaker than normal onshore flow, and minimum temperatures
well above normal will bring less relief than normal overnight. This
will also keep elevated fire weather conditions across the higher
terrain. Even though we are nearing the end of our heat season,
cumulative heat impacts are expected across the interior. With all
that being said, no records are in jeopardy as October is one of the
hottest months for the region. Finally by Thursday, 44% of global
ensemble clusters begin to show signs of a pattern change via
falling heights.
&&
.AVIATION...
(12Z TAFS)
Issued at 442 AM PDT Fri Oct 2 2026
Similar to Thursday morning, conditions vary from VFR inland to
stratus and fog /IFR-LIFR/ along the coastline, in the coastal and
inland valleys. A fair amount of cirrus and perhaps some mid level
clouds are moving up from the southwest associated with upper level
divergence with the merged subtropical jet and southern branch of
the polar jet. These clouds are currently obscuring much of the view
of stratus and fog coverage; the high clouds will be with us through
today. This may delay incoming solar radiative warming and delay
stratus and fog erosion during the morning. Buoy and coastal surface
observations show a fair amount of cool air entrenched within the
marine layer, the marine layer is currently still ~ 1,000 feet deep.
Additional stratus and fog can be seen on satellite moving southward
from northernmost California. The nearest term is a challenging
forecast because of this complex interaction that may lead to a
blending of stratus and fog within a coastal surface trough with
onshore winds by afternoon. Recent (06Z) HRRR output showed coastal
stratus and fog /IFR-LIFR/ continue tonight and Saturday morning;
tonight and Saturday are a long time from now with respect to
stratus and fog forecasting and TAFs. Sometimes it can be difficult
to disrupt stratus and fog in October without well structured
offshore winds, downsloping and drying. The larger scale pattern is
not conducive to widespread offshore winds like it can be in
October; have to approach stratus and fog forecasting a day at a
time since it's complex.
Vicinity of SFO...VFR except tempo stratus /IFR/ 13z-16z this
morning. Stratus /IFR/ likely returns tonight and Saturday morning
10z-18z. Cirrus and perhaps some mid level clouds arrive from the
southwest today, caveat is these clouds may slow stratus development
and mix out today. Light west wind during the morning, shifting to
northwest and westerly 10 to 15 knots in the afternoon and evening.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Stratus and fog /IFR-LIFR/ during the
morning, conditions improving to MVFR-VFR by late morning or
afternoon. Stratus and fog /IFR-LIFR/ return tonight and Saturday
morning. Light and variable winds except cool air drainage winds
5 to 10 knots e.g. in the Salinas Valley during the morning. Winds
shift to onshore 10 to 15 knots in the afternoon and early evening.
Cool air east to southeast drainage winds redevelop tonight and
Saturday morning.
&&
.MARINE...
(Today through Wednesday)
Issued at 353 AM PDT Fri Oct 2 2026
A gentle to moderate northerly to northwesterly breeze will
continue through the weekend and into next week.
&&
.FIRE WEATHER...
Issued at 353 AM PDT Fri Oct 2 2026
Ridging will lead to hot and dry conditions across the region
through the seven day outlook. Daytime humidity retention will
remain poor to very poor away from the immediate coast, while
overnight, the thermal belts remain active and humidity retention
in the higher elevations is poor. Pushes of offshore flow are
possible in the higher elevations each morning. Hazardous heat
builds this weekend, particularly impacting fire crews across the
interior mountains and the Santa Lucia range.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory until 6 PM PDT this evening for CAZ006-
506-508-529-530.
Heat Advisory from 11 AM Saturday to 10 PM PDT Sunday for CAZ503-
504-508-510-512>518.
PZ...None.
&&
$$
SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...Canepa
MARINE...Canepa
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Prepared by Boulder-Creek.com Weather at: Fri Oct 2 06:30:03 PDT 2026
From the National Weather Service
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