FXUS66 KMTR 051009
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
309 AM PDT Mon Oct 5 2026

...New MARINE, FIRE WEATHER...

.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

&&

.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...
(06Z TAFS)
Issued at 944 PM PDT Sun Oct 4 2026

Confidence is mixed as to if stratus/fog will make it to the
coastline tonight. Kept the stratus mention in for HAF but
confidence is decreasing in fog reaching MRY and SNS. Diurnally
breezy winds continue with moderate onshore winds during the day 
and light, variable winds overnight. 

Vicinity of SFO...VFR. Diurnally breezy winds with moderate west
to northwest winds around 16 knots expected during the day before
winds weaken overnight.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Mixed confidence as to if stratus/fog
will reach MRY and SNS tonight. Models are currently
overestimating the eastward extent of the offshore stratus (i.e.
placing it closer to shore) while observations show the stratus
deck to still be well offshore. This is decreasing confidence in
CIG development along the Monterey Peninsula. The wrinkle in this,
however, is that clear skies across the peninsula will allow for
additional radiational cooling and see temperatures dropping
closer to the dewpoint. This would increase the likelihood of fog
development and LIFR conditions. Leaned towards VFR conditions
continuing tonight with some potential for fog to develop early
Monday morning.

&&

.MARINE...
(Today through Saturday)
Issued at 309 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 during the morning. Fog may be locally dense at times.
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 Wednesday for CAZ503-504-506-508-
     510-512>518.

PZ...None.
&&

$$

SHORT TERM...JM
LONG TERM....JM
AVIATION...Canepa
MARINE...Canepa

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Prepared by Boulder-Creek.com Weather at: Mon Oct 5 04:30:04 PDT 2026