434
FXUS65 KBOU 270539
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1139 PM MDT Wed Aug 26 2026

.KEY MESSAGES...

- Scattered afternoon/evening thunderstorms expected for theI-25
  Corridor and plains. A few storms could become severe, with
  large hail and strong winds possible.

- Thunderstorm coverage decreases Thursday and Friday with mainly
  isolated high-based showers/storms with gusty winds.

- Temperatures return to the 90s Friday andSaturday across the
  plains.

- Thunderstorm coverage increases for late Saturday and Sunday.

&&

.DISCUSSION /Through Wednesday/...
Issued at 1140 AM MDT Wed Aug 26 2026

An upper level high will be centered over Arizona/NewMexico
today with ridging extending northward all the way to Alberta.
This will lead to a northwest flow aloft over Colorado. Outflow
from thunderstorms last night and thismorning increased low level
moisture but also cooled the airmass. Temperatures are slow to
warm this morning, with 11 AM readings only in the mid to upper
70s. DEN ACARS soundings still show a strong inversion centered
around 700mb. Forecast model soundings show this as well, but they
don`t appear strong enough regarding the inversion. This leads to
a highly uncertain thunderstorm forecast and severe threat for
later today. MLCAPE is still forecasted to climb to 1000-2000 J/kg
along and east of the I-25 corridor. The 0-6km bulk shear reaches
30-40 knots. The 30 knots is borderline for severe storms, but
where we see east to southeast surface winds around 10 knots, the
bulk shear will be closer to 40 knots. This favors areas east of a
line from Fort Collins to DIA for severe storms. Because of the
slower heating, storm development will likely be delayed with late
afternoonand early evening hours being favored. Again, given the
strength of the inversion, the severe thunderstorm threat remains
highly uncertain.

The upper-level high will remain centered to our southeast, but
the ridge axis shifts eastwardover Colorado on Thursday. This
will bring warmer temperatures and some drying. Precipitable water
valuesfall below an inch throughout the area, except for the far
eastern plains. Warmer air aloft, less moisture and instability
will lead to a notable decrease in thunderstorm activity. There
should be enough lingering moisture for isolated high-based
showers and thunderstorms. Any rainfall is expected to be light,
with gusty outflow winds up to 45 mph possible. However, southeast
winds will prevail over far eastern Colorado, helping to preserve
low level moisture. MLCAPE will reach 1000-2000 J/kg with 0-6km
bulk shear of around 40 knots, which would favor severe
thunderstorms. Warmer air aloft may cap convection, though.
Convergence along a boundary is likely needed for storms to
initiallyform, and models generally don`t show this happening.

The high intensifies (slightly) and drifts northeastward for
Friday. Temperatures warm further, with highs expected to reach
the lower to mid 90s across northeast Colorado. Models hint at a
slight increase in moisture, which should fuel a round of
afternoon/evening showers and thunderstorms. Given the warm
temperatures and limited moisture and instability, the
showers/storms are expected to be high-based with gusty outflows
being common.

For the weekend, an upper level trough (eventually strengthening
into a closed low)will track east across the northwest part of
the country. This will push the upper level high east of the
region, with southwest flow aloft developing over Colorado. We`ll
see an increase in monsoon moisture leading to a better chance for
showers and thunderstorms. The very warm air hangs on for
Saturday with lower to mid 90s expected again, but temperatures
will cool to the mid 80s to lower 90s for Sunday.

The weather pattern for next week starts to look like a late
summer/early fall pattern, featuring stronger west to southwest
flow aloft with one or two shortwave troughs passing across the
region. For now, models show enough moisture each day for a round
of showers and thunderstorms. However, wouldn`t be surprised if we
end up with a dry and breezy day due to subsidence behind an
exiting shortwave trough.

&&

.AVIATION /06Z TAFS through 06Z Friday/...
Issued at 1131 PM MDT Wed Aug 26 2026

VFR conditions expected through the TAF period. Winds are
currently from the southeast at DEN and APA due to an outflow
boundary, however drainage flow should return in the next few
hours. After that, there is some uncertainty with the duration of
drainage flow, but expect a period of light and VRB winds by
14Z/15Z. Winds should turn northeast by early afternoon.

Low confidence remains (20-30%) of showers and thunderstorms
impacting the TAF sites tomorrow afternoon. More likely would see
an outflow boundary through the airports rather than a storm
forming over them. For this reason, have kept the PROB30 in the
TAf and have added variable wind gusts of 25 kts.

&&

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

&&

$$

DISCUSSION...BM
AVIATION...MAI

NWS BOU Office Area Forecast Discussion