436
FXUS65 KBOU 081935
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
135 PM MDT Tue Sep 8 2026

.KEY MESSAGES...

- Slightly cooler today with a chance of thunderstorms mainly over
  the Palmer Divide and southeast plains. A few strong storms
  possible with gusty winds, hail, and locally heavy rainfall.

- Mainly dry Wednesday 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 Tuesday/...
Issued at 1152 AM MDT Tue Sep 8 2026

Upper-air maps show an upper-level low coming off the northern
Rockies along the Canadian border this morning, with another
shortwave close on its heels expected to move over the northern
Rockies later today. An associated cold front made its way into
Colorado early this morning that is keeping temperatures around
five to ten degrees cooler than Monday morning. This should keep
afternoon high temperatures slightly cooler than yesterday, with
only a few places across the plains expected to approach the 90
degree mark. The persistent upper-level ridge over the south
central CONUS will continue to pull a plume of monsoonal moisture
into southeastern Colorado and keep PWATs around 160% of normal
along the southern portion of our forecast area. Areas expected to
see the best precipitation chances will generally be along and
south of I-70, with potential for some strong to severe storms
over the Palmer Divide and across Lincoln County this evening.
With PW values around 1-1.5" expected, we could get a few heavy
rainers that could lead to localized flash flooding potential, and
expect at least an isolated severe wind threat, mainly for Elbert
and Lincoln Counties. The HREF guidance hones in on southern
Lincoln County likely to see the greatest rainfall accumulations,
with the best timing of heaviest rainfall and strong winds between
7PM-10PM. Storms should move out of the forecast area by around
midnight tonight.

Another cold front is expected across northern Colorado early
Wednesday morning that will cool temperatures by a few more
degrees for Wednesday afternoon. Expect some gusty northerly winds
to move from north to south across the plains around sunrise
followed by comfortable afternoon high temperatures at or slightly
below normal. The cooler air isn`t expected to make it into the
higher elevations, so our mountain valleys will likely still see
above-normal afternoon high temps, but still a few degrees cooler
than today. Mid-level flow aloft is expected to become more zonal
as the shortwave passes to the north. This will move drier air
from the west into the forecast area, limiting the monsoonal plume
to southeastern Colorado. Mostly dry conditions are expected for
the forecast area outside of potential for some showers in
southern Lincoln County overnight.

Zonal flow aloft is expected to persist into Thursday keeping
drier air flowing into the forecast area. 700 mb temperatures
should warm by a few degrees resulting in afternoon highs about
five to ten degrees above normal across the forecast area, but dry
conditions are expected. Will have to watch for elevated fire
weather conditions developing for a few hours in North Park
Thursday afternoon where single digit relative humidity values
are expected with wind gusts approaching critical thresholds. Friday
will warm by a few more degrees and latest guidance suggests a
slight increase in mid-level moisture in WNW flow may bring
isolated afternoon showers, but most areas are expected to remain
dry.

The northern tier looks to remain fairly active through the latter
half of the period with multiple disturbances expected to move
across the northern Rockies. This will send a few more cold fronts
south across Colorado this weekend and early next week. Guidance
is still diverging on the strength and timing of a more pronounced
trough moving out of the Pacific Northwest this weekend, but for
now it`s looking like cooler temperatures and more active weather
can be expected for next weekend.


&&

.AVIATION /18Z TAFS through 18Z Wednesday/...
Issued at 1131 AM MDT Tue Sep 8 2026

VFR conditions expected through the TAF period. Easterly winds
have begun filtering into DEN and APA, and have bumped up the
prevailing speeds accordingly. Expect generally an easterly wind
throughout the afternoon, with speeds varying between 08-17 kts.
CAMs still indicate a few high-based storms forming this
afternoon, with the best chance for impacts being at APA. Have
kept a PROB30 in for DEN and BJC due to the threat of gusty
outflow winds of nearby convection. Storms should be out of the
area by 01Z, but there is a chance (

NWS BOU Office Area Forecast Discussion