997
FXUS65 KBOU 211139
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
539 AM MDT Fri Aug 21 2026

.KEY MESSAGES...

- Hot today with high temperatures pushing 100F over portions of
  the plains and I-25 Corridor.

- High-based afternoon and evening showers/storms/virga producing
  gusty microburst winds, with a few strong to severe storms
  possible for the far eastern plains today.

- Monsoon moisture returns this weekend and holds into early next
  week, with increasing chance of storms and slightly cooler
  temperatures.

&&

.DISCUSSION /Through Thursday/...
Issued at 151 AM MDT Fri Aug 21 2026

Another hot day is on tap to end the week as upper-level ridging
continues to dominate the weather pattern, supporting above-normal
temperatures across the forecast area. Afternoon high
temperatures will range from the mid to upper 90s across the
plains, with a few locations reaching 100 degrees. Aside from the
heat, the main concerns for today will be with the development of
isolated to scattered high-based showers and storms as
northwesterly flow aloft allows some mid-level Pacific moisture
to sneak under the amplifying ridge. Expecting convection to
start over the higher elevations in the afternoon and
showers/storms to move southeast onto the lower elevations, where
deep evaporative cooling will likely lead to microbursts and gusty
outflows, with little to no precipitation expected. Gusts between
45 to 55 mph will be possible along the northern portion of the urban
corridor where DCAPE is expected to range from 1300-1700 J/kg.
Farther east, a few strong to severe storms will be possible
across our northeast corner in the evening, where slightly
stronger northwest flow, low-level moisture, and instability will
be in place. While the more robust storms are expected to stay to
our northeast, we can`t rule out seeing a few severe gusts or
hailstones with any stronger storm that develops. The SPC has
issued a Marginal Risk for these hazards for our northeast corner,
which seems reasonable at this time.

Looking into the weekend, the ridge is expected to persist, with a
gradual eastward progression each day. Despite the ridge being
overhead, mid-level moisture is expected to increase. Ensembles
continue to show above normal PWAT values through the weekend,
with the peak expected on Saturday. Surface dewpoints along with
instability both increase on Saturday that will allow scattered to
numerous high-based showers and storms to develop in the
afternoon, and with forecast soundings only showing small
improvements to DCAPE values, storms will be capable of producing
gusty outflows and microbursts once again. Can`t rule out a few
strong to severe gusts with the strongest storms. With regards to
QPF, Saturday looks to be our best chance for more widespread
accumulating rainfall (a few tenths), with a few localized
heavier totals possible. Afternoon high temperatures will cool by
five to ten degrees, with 80s and 90s still expected across the
plains and mountain valleys. Afternoon showers and storms are
expected again on Sunday, though coverage is expected to decrease
compared to Saturday, with the higher elevations having the best
chance for a few hundredths to around a tenth of an inch. Another
day of afternoon high temps in the 90s is expected across the
plains, with a slight cooldown for the mountain valleys.

A shortwave passing over the Northern Rockies on Monday is
expected to flatten the ridge for a day or two, bringing a slight
cool down for mid-week. Afternoon showers and storms are expected
to persist each afternoon through the forecast period, with the
NBM pointing to another warming and drying trend returning by the
second half of the week.

&&

.AVIATION /12Z TAFS through 12Z Saturday/...
Issued at 531 AM MDT Fri Aug 21 2026

A boundary just pushed across KDEN/KAPA that temporarily disrupted
the drainage winds and turned things to the southeast. This is
expected to reach KBJC by around 1230Z. Things are already working
their way back to the southwest, but it may take about an hour to
get back there. Winds are still expected to make their way to the
NNE at KDEN/KAPA, with KBJC staying slightly more NE by 18Z-19Z.

The main concern for today continues to be with the potential for
high-based showers capable of producing gusty outflows and some
dry microbursts. Despite the low potential for any precipitation
(~15% chance) at any of the TAF sites, there will be ample amounts
of DCAPE in the area that will support some strong microbursts as
showers move off the higher terrain through the afternoon. Even if
showers do not pass directly over the TAF sites, gusty outflows
are expected to impact the TAF sites, bringing potential for
multiple wind shifts through the afternoon, with gusts up to 30-40
kts possible. The greatest coverage in showers looks to be north
of the TAF sites in the afternoon, that will aid in keeping winds
more northerly, but certainly can`t rule out wind shifts from
other directions where showers develop. A PROB30 remains in all
TAFs to account for this, but has been pushed back an hour based
on latest guidance. As showers progress eastward in the evening,
winds should turn to the east before turning to the south and then
drainage for the overnight. We can`t rule out a few easterly
outflows making it back to the TAF sites through the evening, as a
few stronger storms are expected to develop over the eastern
plains.

&&

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

&&

$$

DISCUSSION...9
AVIATION...9

NWS BOU Office Area Forecast Discussion