617
FXUS65 KBOU 091913
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
113 PM MDT Wed Sep 9 2026

.KEY MESSAGES...

- Tranquil weather expected across the forecast area today with
  slightly below normal temperatures across the plains.

- Mainly dry through Friday with warmer temperatures for Thursday
  and Friday.

- Return to more unsettled pattern and cooler weather favored for
  next weekend with a chance of thunderstorms each afternoon.

&&

.DISCUSSION /Through Wednesday/...
Issued at 1251 PM MDT Wed Sep 9 2026

A quiet day is expected across the forecast area today behind this
early morning`s cold front. Dare we say that fall is trying to make
itself known, despite a few more 90 degree days lurking in our
forecast?

For today, temperatures will be at or slightly below
normal across the plains with the cooler air mass in place. The
cooler air won`t pack enough of a punch to make it to our mountain
valleys, where afternoon high temps will still remain about five to
ten degrees above normal. As evident on water vapor imagery, much
drier air will be in place across the forecast area, as westerly
flow aloft will keep the monsoonal moisture plume flowing into
southeastern Colorado, on the periphery of our southern most
counties. CAMs show storms developing along a cold front in
southeastern Colorado tonight. A few may manage to move north into
southern Lincoln County late tonight. With PW values around 1-1.5",
any storms that do move into the area will be capable of some heavy
rainfall.

Warm and dry conditions are expected on Thursday as flow aloft turns
more northwesterly, and 700 mb temps warm a few degrees. This will
translate to a few degrees of warming at the surface, bringing
afternoon high temps back to above normal across the forecast area.
Relative humidities will drop into the single digits in our high
mountain valleys and there will be some patchy elevated to near
critical fire weather conditions, mainly for North Park and some
localized areas along the Continental Divide.

Mid-level moisture will start to work its way back into the area on
Friday as a shortwave moves across the northern Rockies and flow
aloft becomes more westerly, once again. There may be enough
moisture in place for some high-based showers in the
afternoon/evening, but instability looks lacking for anything
substantial at this time. Folks across the plains have a good shot
at ending their work week with temperatures at or around the 90
degree mark before another cold front slides south across Colorado
Friday night that will bring Saturday`s high temps back closer to
normal.

The northern tier will remain active through the weekend, with a
more pronounced shortwave expected to move into the Pacific
Northwest on Saturday and traverse the northern Rockies on Sunday.
This will turn flow aloft slightly more southwesterly through the
day on Saturday and allow us to tap back into some mid-level
Pacific moisture. Afternoon showers and storm activity will
increase, with isolated to scattered showers/storms possible each
afternoon. One more summerlike warmup is expected on Sunday, with
afternoon highs warming into the low to mid 90s along the urban
corridor. Another cold front will push south Sunday night cooling
things back down to near normal temperatures for Monday. The
forecast high for Denver International Airport is 93 degrees on
Sunday, which would put us within a few degrees of the record high
for this day (96 is the current September 13th record, last set
in 2018). Looking at ensembles, this may end up being one of, if
not the last 90 degree day of the season, as there is a definite
trend of cooler temperatures (sub 90 degrees) present in the
latest ensemble outputs (though there is certainly plenty of time
for this to change!).

&&

.AVIATION /18Z TAFS through 18Z Thursday/...
Issued at 1134 AM MDT Wed Sep 9 2026

VFR conditions expected throughout the period. Winds are expected
to stay under 15 kts. Typical diurnal winds are expected for
today and tonight with only a few upper-level clouds. Tomorrow
morning, winds will briefly be VRB before turning to ESE in the
afternoon. No precipitation is expected today or tomorrow.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...9
AVIATION...MV

NWS BOU Office Area Forecast Discussion