552
FXUS65 KBOU 251129
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
529 AM MDT Tue Aug 25 2026

.KEY MESSAGES...

- Scattered afternoon and evening showers and storms through at
  least Thursday. A few storms could become severe, particularly
  on Wednesday.

- Slightly cooler with near normal temperatures today and
  Wednesday.

- Gradual drying and hotter temperatures by Friday and the
  weekend, but a few storms still possible.

&&

.DISCUSSION /Through Monday/...
Issued at 237 AM MDT Tue Aug 25 2026

The next few days will be a bit active in the afternoon and
evening hours, with daily chances of showers and thunderstorms
for the Front Range mountains and plains. Temperatures will be
slightly cooler today due to a weak frontal boundary moving
through the area, associated with an upper level shortwave. We
will likely stay just shy of 90 dg, with highs in the upper 80s.
With upslope flow by late morning, showers and thunderstorms will
develop of the Front Range mountains by around noon before
spilling onto the I-25 Corridor and adjacent plains. Instability
does not look impressive immediately off the foothills, so storms
should stay below severe limits. However, with steep surface-to-3
Km lapse rates, and DCAPE values of 1200- 1400 J/kg, gusty
outflow winds of 40-50 mph is possible. As these storms track
further east, they will be able to tap into better moisture and
thus better instability. While the best chance for severe storms
should be east of Colorado, cannot rule out a few becoming severe
across the eastern plains. Hail and strong outflow winds will be
the main concerns.

The "cooler" temperatures should last though Wednesday, with highs
forecasted to be in the mid/upper 80s across the plains. With
easterly flow at the surface, low-level moisture will be advected
further west towards the I-25 corridor and instability will build.
Upslope flow once again will allow thunderstorms to form over the
Front Range mountains and spill onto the plains by the mid-to-late
afternoon. With decent shear due to increased flow aloft, chances
are increasing for supercell development with large hail and strong
outflow winds as the main threats. As of now, guidance favors best
shear/instability profiles just east of the Denver metro, but will
continue to monitor trends. SPC has introduced a Slight Risk (2/5)
for Denver and portions of the eastern plains, which seems
reasonable at this time. There is also an isolated threat of locally
heavy rainfall, given the uptick in low-level moisture.

We will begin to warm up again on Thursday as the axis of the mid-
level thermal ridge shifts slightly towards the forecast area. There
will still be enough moisture and instability to support another
round of scattered afternoon showers and thunderstorms. Towards the
eastern plains, more favorable instability and shear profiles could
support a few storms becoming strong/severe.

Ensemble guidance continues to favor heat rebuilding over the area,
with temperatures reaching back up to the mid-90s by Friday and
Saturday. With the upper level ridge flattening and shifting east
over Colorado due to a shortwave in the northwest, moisture will
be cut of. However, there should still be enough lingering low-
level moisture to support a few afternoon storms. Expect coverage
to be more limited. Some cooling returns by Sunday or Monday, with
chances of showers and thunderstorms increasing by the beginning
of next week.

&&

.AVIATION /12Z TAFS through 12Z Wednesday/...
Issued at 519 AM MDT Tue Aug 25 2026

VFR conditions expected through the TAF period. After the passage
of a frontal boundary, winds are currently light and VRB at all
TAF sites. Expect light (generally under 8 kts) winds to continue
this morning, before northeast winds filter in by the late
morning/early afternoon. Upslope flow will promote scattered
showers and thunderstorms this afternoon, erratic outflow winds of
30-40 kts impacting the airports by 21Z at BJC and 22Z as DEN and
APA. Guidance is in good agreement that convection should exit the
area by 01Z.

There is some uncertainty with wind direction behind convection.
For now, have opted in for an easterly wind direction before
light drainage flow returns. Guidance does favor light and VRB
winds by early Wednesday morning. If these winds have an easterly
component to them, low clouds/patchy fog could impact the
airports. Have kept any mention of it out of the TAF for now, but
will need to continue to monitor.

&&

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

&&

$$

DISCUSSION...MAI
AVIATION...MAI

NWS BOU Office Area Forecast Discussion