417
FXUS65 KBOU 210644
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1244 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 late afternoon and evening showers/storms/virga
  producing gusty microburst winds, with a few strong to severe
  storms possible for the far eastern plains.

- 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 133 PM MDT Thu Aug 20 2026

A warmer and drier airmass is taking hold today as the ridge
starts to amplify over the Four Corners into the Great Basin. We
still have enough moisture per current satellite imagery for a few
showers and weaker storms in the mountains, mainly south of I-70.
Those will end early this evening as the airmass stabilizes,
while the plains will remain too dry and stable for any convective
activity. Overnight lows will be several degrees above normal.

On Friday, we`ll be back to the frying pan as the thermal ridge
shifts eastward and centers itself across Colorado. 700 mb
temperatures warm a couple more degrees C, which supports highs in
the mid to upper 90s across the plains and I-25 Corridor, with a
few spots nearing 100F from downtown Denver to Greeley and Fort
Collins. The record for tomorrow in Denver is 99F set in 2023,
and we should be very close to that at the official reporting
station. Those readings also bring us very close to Heat Advisory
criteria, but most locales should stay just below 100F. There will
be some heat relief in the form of high based convective clouds
late in the day as mid/upper level moisture starts to spread into
the region. Given large DCAPE of 1500-1700 J/kg and deep
inverted-v profiles, strong microburst winds to 50+ mph will be
possible from any high based showers.

For the weekend, ensembles are still showing the upper level ridge
axis to shift slowly eastward or flatten, with the flow aloft
trending more westerly. This will allow for an uptick in monsoonal
moisture across the forecast area, leading to scattered thunderstorms
each afternoon. In these moisture and flow patterns, the most
numerous storms are expected over the mountains and eastern
plains. Meanwhile, the majority of the storms along the I-25
Corridor will be higher based as the airmass is still quite warm
and low level moisture is expected to be lacking. But given the
uptick in precipitable water to near 150% of normal, that still
doesn`t mean we can`t see locally heavy rainfall.

There may be some change in this pattern as flow turns slightly
more west-northwesterly toward Tuesday or Wednesday. That could
allow for a weak backdoor front or two with increasing low level
moisture, but plenty of uncertainty exists here with respect to
timing and intensity of any surge(s). In any case, it appears
temperatures will settle a little closer to (still above) normal
for this weekend through much of next week. And enough moisture
will be around to keep a chance of storms in the forecast most
days.

&&

.AVIATION /06Z TAFS through 06Z Saturday/...
Issued at 1207 AM MDT Fri Aug 21 2026

Southerly drainage winds have settled in at KDEN and KAPA late
tonight, with light and variable winds in place at KBJC. Expecting
winds to become slightly more southwesterly at KDEN/KAPA by 13Z to
14Z, with KBJC holding onto a light northwesterly flow by around
10Z tonight. Winds are expected to transition to the NNE at
KDEN/KAPA by 18Z-19Z, with KBJC being slightly more NE.

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. 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...20
AVIATION...9

NWS BOU Office Area Forecast Discussion