FXUS66 KMTR 051633
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
933 AM PDT Mon Oct 5 2026
...New UPDATE, MARINE...
.KEY MESSAGES...
Updated at 1213 PM PDT Sun Oct 4 2026
- Hazardous heat conditions persist inland, never leave children
or pets in unattended vehicles!
- Elevated fire weather conditions continue across the interior
through Thursday
- Temperatures cool closer to normal for the end of the week
into next weekend
&&
.UPDATE...
Issued at 930 AM PDT Mon Oct 5 2026
With increasing confidence in heat impacts continuing through
Thursday, the Heat Advisory has been extended through 10 PM
Thursday for the inland regions of the Bay Area and Central Coast.
Despite a couple degrees of cooling from Wednesday's highs, the
cumulative heat impacts will continue and a moderate risk of heat-
related illnesses continues into Thursday.
DialH
&&
.SHORT TERM...
Issued at 1230 AM PDT Mon Oct 5 2026
(Today and tonight)
The weak upper level disturbance embedded in the broader scale
ridging can be seen on satellite shifting inland overnight.
Unfortunately it offers no relief in cooling temperatures and will
reinforce offshore flow as it continues to exit east during the day
today. A Heat Advisory remains in effect for most of our area
through Wednesday night, however the advisory for the immediate
coastline from Sonoma County south to Santa Cruz County was allowed
to expire on schedule. Todays high temperatures will continue to run
15-25 degrees above normal with overnight lows generally running 10-
20 degrees above normal, offering little to no night time relief to
the moderate to major HeatRisk we'll see through Wednesday across
the interior. Despite a return of stratus along the coastline,
expect the marine layer to continue to hold primarily to the coast
today while remaining compressed and fighting fetches of offshore
flow.
Follow these tips to avoid heat exhaustion and heatstroke:
* Stay hydrated and drink plenty of fluids.
* Wear lightweight, light-colored clothing.
* Reduce time spent outdoors or stay in the shade.
* Never leave people or pets unattended in vehicles.
* Use sunscreen if going to the coast or the pool.
&&
.LONG TERM...
Issued at 1230 AM PDT Mon Oct 5 2026
(Tuesday through Sunday)
The synoptic scale ridging across our region will be reinforced
through mid-week in the wake of the weak upper level system to our
north exiting east today. Temperatures today through Wednesday will
be very similar with little day to day variability for most
locations. Another weak upper level system develops offshore for the
middle to end of the upcoming work week, and will combine with a
more potent disturbance embedded in the polar jet to begin to lower
H50 heights by Thursday with a return to more normal temperatures
for the end of the week into the weekend, when daytime highs are
expected to fall back to or below normal by the weekend.
&&
.AVIATION...
(12Z TAFS)
Issued at 435 AM PDT Mon Oct 5 2026
It's VFR except for a slowly and steadily eastward moving shallow
layer of low stratus and fog /LIFR/ reaching the coastline.
Because the marine layer is compressed to ~ 500 feet, fog may be
locally dense with surface visibilities reduced to less than 1/4
mile. The vast area of fog represents cooler air relative to sea
surface temperatures; nocturnal radiative cooling through daybreak
will help fog /LIFR/ form as well. Nocturnal radiative cooling
will also produce light cool air drainage winds in some of the
valleys through daybreak. However, there is also a weak onshore 1
mb SFO-SAC pressure gradient, with no sign of offshore wind at
Angel Island at this hour, the wind there has been southwesterly
around 16 mph. Just away from the shallow marine layer farther
inland and at higher elevations it's still warmer (like Sep and Oct
can be) by up to 30F greater this morning within the lower level
temperature inversion.
Because of the shallow marine layer depth and strength of lower to
mid level thermal ridging, inland areas will stay VFR during the
12z TAFs. Along the coast expect fog to mix out by later morning,
with potential for low stratus and/or fog /IFR-LIFR/ returning
tonight and Tuesday morning.
Vicinity of SFO...VFR. West wind 5 to 15 knots, strongest in the
afternoon to mid evening.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...It's currently VFR, however expect low
stratus and/or fog, possibly dense fog /IFR-LIFR/ forming through
daybreak. Diurnal warming will mix out the fog later in the morning
with VFR from late morning through afternoon. Expect at least
patchy low stratus and/or fog /IFR-LIFR/ tonight and Tuesday
morning. Light southeast winds shifting to onshore 5 to 15 knots
by late morning to early afternoon. Winds decreasing to less than
10 knots and becoming light land breezes again late tonight and
Tuesday morning.
&&
.MARINE...
(Today through Saturday)
Issued at 930 AM PDT Mon Oct 5 2026
An extensive low stratus and fog layer is steadily advancing
eastward across the coastal waters and will reach much of the
coastline throughout the morning and into the afternoon. A gentle
to moderate breeze and slight to moderate wave heights persist
into midweek. Winds increase and wave heights build, seas becoming
rough across the outer waters, Friday into the weekend.
&&
.FIRE WEATHER...
Issued at 306 AM PDT Mon Oct 5 2026
Strong ridging aloft will lead to hot and dry conditions through
Thursday with elevated fire weather conditions across the higher
elevations. Poor to very poor overnight humidity recoveries will
continue across the thermal belts with pushes of offshore flow
each morning. Hazardous heat will continue through Thursday with
major to extreme risks of heat-related illnesses across most
mountain ranges. A pattern change later this week will bring
cooler conditions to the region.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 10 PM PDT Thursday for CAZ503-504-506-508-
510-512>518.
PZ...None.
&&
$$
SHORT TERM...JM
LONG TERM....JM
AVIATION...Canepa
MARINE...RGass
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Prepared by Boulder-Creek.com Weather at: Mon Oct 5 10:30:03 PDT 2026
From the National Weather Service
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