430
FXUS65 KBOU 222359
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
559 PM MDT Mon Jun 22 2026

.KEY MESSAGES...

- Strong to severe storms expected for the plains this afternoon,
  producing large/very large hail, gusty winds, and possibly a
  weak landspout.

- Additional rounds of severe storms expected Tue-Wed, with
  increasing potential for impacts to I-25 corridor and localized
  flash flooding. Temperatures to remain slightly below normal.

- Elevated to locally critical fire weather conditions in the
  mountains most afternoons, increasing in severity this weekend
  under building heat and strengthening winds.

- Drier and considerably hotter for the lower elevations starting
  Friday.

&&

.DISCUSSION /Through Monday/...
Issued at 230 PM MDT Mon Jun 22 2026

Current observations show thunderstorms starting to develop over the
east Colorado plains. The Denver Convergence-Vorticity zone (DCVZ)
is currently situated just east of the Denver metro, which is
providing an area of enhanced surface vorticity. Bulk shear values
over eastern Colorado are in currently in the 40-50KT range,
although the better 0-3 km storm relative helicity (SRH) values are
located over our northeastern CWA counties. Nevertheless, the
aforementioned parameters, combined with precipitable water (PW)
values around 0.70"-1.00", and steep lapse rates (~8 C/km), will
support the development of supercells able to produce large hail,
gusty winds, and weak landspouts. Localized flash flooding will also
be a concern with any slow-moving storms this afternoon, as well
as over the next few days, especially over areas with leftover
soil moisture from the previous day`s storms. While the primary
thunderstorm threat will likely be out of the area by 7pm,
additional elevated thunderstorms cannot be ruled out later in the
evening, as we have seen occur over the last few evenings where
outflows from farther east have triggered convective initiation.

A cold frontal passage is expected to bring northerly flow into the
region Tuesday morning, as well as the potential for some patchy low
clouds. Severe thunderstorms will be possible again tomorrow.
However, the initial convective environment will face a few more
challenges earlier in the day, given the slightly drier surface
dewpoints behind the front, and northerly winds, as opposed to the
moister southeasterly flow that is in place today. However, the
shear profile tomorrow looks to be more favorable for rotating
updrafts, with high-res model soundings showing curved hodographs,
and a few isolated but longer-lived supercells. All hazards will be
possible with any storms that develop tomorrow afternoon and
evening, although the primary concern is very large hail (>
2.00").

Wednesday and Thursday will bring more rounds of severe weather
potential (mainly hail), driven by zonal flow aloft and low-level
moisture advection from the southern U.S. plains. The PW content in
place over the Denver area through most of this week is at the
90th percentile of climatology for late July, which is when the
annual peak of PW values occurs. However, the high terrain to the
west is a different story, given that this surge in moisture will
be confined to the low elevations of eastern Colorado and the
foothills. As such, elevated to locally critical fire weather
conditions will persist over the mountains and high valleys where
relative humidities will drop into the teens and single digits
each afternoon, with winds gusting to 20-35 mph.

Widespread critical fire weather conditions are still on track to
arrive on Saturday as an approaching upper level trough pushes
the moist airmass in place eastwards while also causing winds to
increase due to the tightening pressure gradient.

&&

.AVIATION /00Z TAFS through 00Z Wednesday/...
Issued at 555 PM MDT Mon Jun 22 2026

The DCVZ has been located east of KDEN for much of the afternoon
sparking off showers and thunderstorms mainly to the east of KDEN
and KAPA. TSRA development and strong gusty outflow winds remain
possible at KAPA and KDEN until at least 02z this evening so have
extended the prob30.

Wildfire smoke is possible overnight, potentially impacting
slantwise visibility at times, but currently looks to have minimal
near surface impacts. Winds should stay elevated this evening
with gusts as high as 25 kts given the continued outflow enhanced
winds especially at KDEN and KAPA. A front will push through from
north to south for all three terminals between 13z and 15z
tomorrow morning with gusty winds from the north. This will also
bring in low stratocu clouds as noted in Bufkit soundings and
relative humidity cross sections. There is an increasing chance of
IFR conditions or worse between about 13z and 17z on Tuesday
morning.

By tomorrow afternoon, winds should settle into a more NE
direction. Showers and thunderstorms are possible especially at
KDEN tomorrow afternoon with the threat for gusty outflow winds
once again, but there is low confidence in exact placement and
timing of thunderstorms at this time.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon to 8 PM MDT Tuesday for COZ212-213-
217.

&&

$$

DISCUSSION...AA
AVIATION...MV

NWS BOU Office Area Forecast Discussion