638
FXUS65 KBOU 081737
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1137 AM 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 mainly on Sunday.

&&

.DISCUSSION /Through Monday/...
Issued at 239 AM MDT Tue Sep 8 2026

The flow aloft will become more WSW today as best monsoon
moisture shifts mainly across srn portions of the area. Meanwhile,
a secondary surge of drier air in the lower levels will move
across the plains. By aftn, MLCAPE will range between 500-800 j/kg
and be confined to the srn foothills, Palmer Divide and over sern
portions of the CWA. With decent shear in place, can`t rule out a
few stronger storms in this area by late aftn thru the early
evening hours. PW values will still be around 150 percent of
normal, in the same general area, so may see locally heavy
rainfall as well. Over the rest of the area, shower and tstms will
be more isolated in coverage. Highs today will drop back into the
mid to upper 80`s across the plains.

For Wed, drier in westerly flow aloft will be over the area as a
cold front move across.  As a result, expect dry conditions with
cooler temps as highs finally drop back to more seasonal levels.
By Wed night, low level southeast flow will develop which will lead
to some return of moisture across the plains.  Meanwhile, a weak
disturbance embedded in WNW flow aloft may bring some nocturnal
tstms to portions of the sern plains overnight.  Current data, keeps
most of this activity over sern CO with srn Lincoln county being on
the nrn fringe. For now, have kept in chc pops mainly across srn
portions of Lincoln county.

On Thu, the flow aloft will remain WNW as southerly level flow is
across the plains.  MLCAPE will rise up to 1000 j/kg over portions
of the plains by aftn.  For now, chances for tstms look on the low
side as I can`t find a focus for activity, however, that doesn`t
mean there couldn`t be an isold storm or two across the plains by
late aftn. Meanwhile, temps will begin to warm as readings reach
the upper 80`s to lower 90`s over nern CO.

Looking ahead to Fri, zonal flow aloft will be over the area as a
sfc lee trough develops over the plains.  This will lead to another
warm day as highs rise into the upper 80`s to mid 90`s over the
plains.  Meanwhile, models have some mid level moisture embedded in
the flow, which may lead to a slight chc of higher based
showers/tstms over the higher terrain. Across the plains, MLCAPE
is rather minimal so chances of precip look low.

For Fri night into Sat, zonal flow aloft will continue.  Meanwhile,
a cold front will move across Fri night into Sat morning.  This
front will drop temps back to more seasonal levels across nern CO.
Once again MLCAPE is rather minimal and confined to the higher
terrain.  Thus will keep in a slight chc for showers/tstms
mainly across the mtns.

By Sun, an upper level trough will move into the nrn Rockies with
increasing WSW flow aloft across the area.  At the sfc, a lee trough
will intensify east of the mtns with southerly low level flow across
the plains.  MLCAPE is fcst to increase to around 1000 j/kg over the
plains east of a pseudo dryline.  Thus may see a few stronger storms
by late aftn thru the evening hours.  Highs on Sun, will likely rise
back to above normal levels.

Looking ahead to Mon, rather dry WSW flow aloft will be over the
areas a cool front affects the plains.  Latest data, doesn`t show
much low level moisture behind the front so it may end up dry with
temps dropping back to seasonal normals.

&&

.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 (<30% chance) of a lingering
shower through 02Z, particularly for APA.

A more southerly drainage wind expected overnight tonight (around
180-190 degrees). Models are in good agreement of the cold front
now arriving between 11Z-13Z, which will bring northerly winds
(northeasterly for BJC) to the terminals. There could be a period
of gustier northerly winds in the morning for DEN, so have
introduced a TEMPO for that reason between 13Z-15Z. Expect a
typical diurnal pattern tomorrow afternoon. With drier air
filtering in, no precipitation is expected for the terminals.

&&

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

&&

$$

DISCUSSION...RPK
AVIATION...MAI