FXUS66 KMTR 080651
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1151 PM PDT Mon Sep 7 2026

...New SHORT TERM, LONG TERM, KEY MESSAGES...

.KEY MESSAGES...
Updated at 1130 PM PDT Mon Sep 7 2026

  - Warming and drying trend will bring widespread moderate to 
    major HeatRisk through Thursday

&&

.SHORT TERM...
Issued at 1151 PM PDT Mon Sep 7 2026
(Tonight through Wednesday)

24 hour trends are warmer and drier. Already a warming trend is 
underway with increasing thermal and height ridging aloft. Any
marine layer influence is confined to within a few hundred feet 
of sea level with only a few patches of fog along the Big Sur 
coast at the moment.

The large scale pattern shift to warmer/hotter temperatures 
involves both the retrogression (westward motion) of the 
subtropical ridge over the central U.S. and the eventual merging 
of tropical energy and moisture from steadily decaying TS Marie 
and a cut-off low far to our west (also forecast to retrogress). 
Strengthening 500 mb heights, large scale compression and the Sep 
sun angle will raise temperatures up further Tuesday, peaking well
above normal both Wednesday and Thursday. A little bit of a 
wildcard to this week's pattern is the northward intrusion of 
tropical moisture including some warm air advection (far from 
decaying TS Marie) which will be west of the 500 mb ridge axis. 
Higher to much higher precipitable water will arrive here, model 
forecasts are still showing near 1.40" in the Bay Area mid-week, 
near the max moving average for Oakland upper air early-mid Sep 
climatology. Mid and high clouds will increase, but we don't 
really know quite yet with high confidence how well the models may
or may not be handling mid-level convective potential (mucape) 
with disagreement among various output from e.g. from the HRRR and
GFS. Good to see the GFS shows very minimal to no mucape anyhow. 
Also, with hotter surface temperatures (greater internal energy) 
air parcels will stay capped as long as the atmosphere is stable.

Hot temperatures for this week are not quite in reach of long term
record highs at this point, except Half Moon Bay may get close if
there's no shallow sea breeze mid-week as an offset to the 
temperature. Will continue to monitor.

A Heat Advisory is in effect for the entire forecast area from 10
AM Wednesday to 10 PM Thursday. We've had a nice 10 to 11 day run
of below normal temperatures (due to a large scale trough), 
especially inland, so the sudden reversal in temperatures will be 
noticeable if not already. With widespread moderate to major 
HeatRisk, this affects most individuals sensitive to heat, 
especially those without effective cooling and/or adequate 
hydration. Please stay out of direct sunlight, and stay properly
hydrated. Hot conditions can cause heat illnesses.

Also, minor coastal flooding is likely within a small window of 
time of about 1 hour nearest high tide Tuesday (possibly Wednesday
as well) for bayshore locations of Marin County. Impacts will 
include minor flooding of the lowest lying areas directly along 
the shoreline. At the San Francisco tidal gauge, high tide is 
expected to be 1 ft above normal at 9:59 PM 9/8. At this time we 
are messaging it here and will include messaging in social media 
vs issuing a coastal flood advisory for Monday.

The Beach Hazards Statement was allowed to expire.

&&

.LONG TERM...
Issued at 1151 PM PDT Mon Sep 7 2026
(Wednesday night through next Monday)

Well above normal hot weather continues Thursday. Thereafter
northwest winds and a gradual weakening of the 500 mb ridge will
bring a cooling trend for late in the week and weekend. Daytime
highs will cool back to near normal Friday, then possibly a few
degrees below normal for the upcoming weekend. Late week weather
will be dry with the mid-latitude pattern settling back in.

&&

.AVIATION...
(06Z TAFS)
Issued at 934 PM PDT Mon Sep 7 2026

It's VFR except satellite imagery shows a few patches of stratus 
and fog over the southern coastal waters. VFR continues during the 
06z TAF cycle except for radiative cooling tonight resulting in 
additional patchy low stratus and fog /IFR-LIFR/ tonight and early 
Tuesday morning. Winds a mix of light onshore and offshore tonight 
and Tuesday. 

Vicinity of SFO...VFR. West wind 10 to 15 knots becoming light and
variable to light northeast tonight and Tuesday morning. Wind
shifting to northwest 8 to 12 knots Tuesday afternoon and early
evening. 

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR except patchy low stratus and fog
/IFR-LIFR/ developing nearby tonight and Tuesday morning. VFR
Tuesday afternoon and evening. Winds mainly light and variable
tonight and Tuesday morning, then west to northwest near 10 knots
Tuesday afternoon and early evening. 

&&

.MARINE...
(Tonight through next Sunday)
Issued at 924 PM PDT Mon Sep 7 2026

Northwest winds gradually diminish to gentle to moderate tonight
which then prevails through the remainder of the week. Northwest
winds look to increase late this week into the weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement until 11 PM PDT this evening for CAZ006-
     505-509-529-530.

     Heat Advisory from 10 AM Wednesday to 10 PM PDT Thursday for 
     CAZ006-502>506-508>510-512>518-528>530.

PZ...None.
&&

$$

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

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Prepared by Boulder-Creek.com Weather at: Tue Sep 8 00:30:03 PDT 2026