727
FXUS65 KBOU 201113
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
513 AM MDT Mon Jul 20 2026

.KEY MESSAGES...

- Hot weather continues today, with highs pushing near 100F over
  the I-25 Corridor and adjacent plains. A Heat Advisory remains
  in effect for the Denver Metro/I-25 corridor through 9 PM this
  evening.

- Scattered afternoon/early evening storms in the mountains
  expected today, with the plains remaining dry.

- Arrival of monsoonal moisture by Tuesday which will continue
  through Thursday. Storms from Tuesday through Thursday will be capable
  of producing locally heavy rainfall.

- Only a slight cooling trend forecast this week with the arrival
  of better moisture.


&&

.DISCUSSION /Through Sunday/...
Issued at 302 AM MDT Mon Jul 20 2026

An upper level high will still reman over the area today with very
hot temps as readings reach the upper 90`s to lower 100`s across
nern CO.  Meanwhile, satellite imagery continues to show some influx
of monsoon moisture across nrn portions of the CWA.  PW values are
fcst to be around 150% above normal over the nrn mtns this aftn.  As
a result, will see sct showers and tstms across portions of the
higher terrain with localized areas of heavier rainfall as storms
will be slow moving.  Across nern CO, it will be dry this aftn.
However, by early evening an outflow boundary may come off the
higher terrain so can`t rule out a slight chc of showers and storms
along nrn portions of the I-25 Corridor.

On Tue, the upper level high will weaken a bit and shift some what
to the southeast. As a result, this will allow for monsoon
moisture to move into most of the area with weak flow aloft.
Meanwhile, a cool front will move across nern CO late tonight
into Tue morning with easterly low level flow. As a result, it
won`t be as hot across the plains as readings drop into the upper
80`s to mid 90`s for Tue aftn. As fas as precip, will see sct slow
moving showers and storms in the aftn over the higher terrain. PW
values will be 150% to 175% above normal over the higher terrain
so expect some heavier rainfall in some areas. As far as the
plains, outflow boundaries from tstms over the higher terrain will
move across the I-25 Corridor by late aftn or early evening. As a
result, should see additional tstm activity develop by late aftn
or early evening from Denver north to the WY border. With
increasing ESE low level flow Tue evening along with PW`s above
150% may see heavier rainfall across nrn portions of the I-25
Corridor.

For Wed, will continue to see monsoon moisture moving across the
area as the main upper level high is centered to the southeast of
the area.  PW`s across the high terrain will be from 150% to 200%
above normal so expect areas of heavier rainfall during the aftn
with the stronger storms.  Across the plains, the low level flow
will become southeast so expect a Denver cyclone to develop by aftn.
Should see tstms develop along the associated convergence zone with
storms moving slowly to the east from late aftn thru the evening
hours. Once again with PW`s aoa 150% or normal expect areas of
heavy rainfall. Highs on Wed, will remain in the upper 80`s to mid
90`s over nern CO.

By Thu, monsoon moisture will continue over the area as a weak upper
level trough moves across Thu aftn and night.  PW`s are still fcst
to be from 150% to 200% above normal.  Thus should see another round
of showers and storms across much of the area with areas of heavy
rainfall.  Highs on Thu will be in the upper 80`s to lower 90`s
across the plains.

Looking ahead to Fri and Sat, the upper level high will gradually
build back into the area as monsoon moisture decreases.  As a
result, will see lower tstm chances both days with warmer
temperatures. Highs across nern CO will rise back into the 95 to 100
range by Sat.

&&

.AVIATION /12Z TAFS through 12Z Tuesday/...
Issued at 510 AM MDT Mon Jul 20 2026

Winds will become light and variable by 14z. By 18z winds will
become east and then become more ESE by 22Z. Outflow boundaries
from tstms over the higher terrain may move across by 01z which
could lead to a 20 percent chc of tstms thru 04z. Thus have
included a Prob30 for this scenario. By late evening winds will
be SE and then switch to drainage by 07z.  A cool front will move
into the area by 12Z Tue with winds becoming northerly.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 9 PM MDT this evening for COZ038>040-043.

&&

$$

DISCUSSION...RPK
AVIATION...RPK

NWS BOU Office Area Forecast Discussion