039
FXUS65 KGJT 210555
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1155 PM MDT Thu Aug 20 2026

.KEY MESSAGES...

- Scattered storms capable of producing gusty outflow winds and
  lightning develop over the high terrain on Friday.

- Thunderstorm coverage increases this weekend with monsoonal
  moisture moving in. Flash flooding will be possible,
  especially Saturday.

- Temperatures remain 5-10 degrees above normal through the
  seven-day forecast, with Friday looking to be the warmest day.

&&

.DISCUSSION...
Issued at 1029 PM MDT Thu Aug 20 2026

HOT WITH MOUNTAIN STORMS ON FRIDAY:

High pressure remains anchored over the Four Corners region on
Friday, providing another day of scattered showers and
thunderstorms mainly over the high terrain. The main concerns
with any storm activity remain gusty outflow winds to 35 mph and
lightning with some localized wetting rain in the stronger
convection. While hydro concerns will be minimal through Friday
due to the drier low levels, stronger convection could result in
a localized flash flooding threat over burn scars and
susceptible terrain.

As we close out the work week, unseasonably warm temperatures
remain in place with triple digits possible in many desert
valley locations. Elsewhere, look for temps to remain about 10
degrees above normal until we hit the weekend.

WET WEATHER RETURNS THIS WEEKEND:

Wetter weather returns to the region on Saturday as low
pressure pushes inland across the Pacific Northwest and nudges
the ridge overhead eastward, putting eastern Utah and western
Colorado in a more favorable trajectory for monsoonal moisture.
While the strongest fetch of moisture will remain further west
across the Great Basin, PWATs will increase to 150-175% of
normal. Flash flooding impacts become more probable during this
period as a robust shortwave moves through the southerly flow
late Saturday afternoon into the evening. This added forcing,
combined with the uptick in moisture, will likely result in
widespread storm activity late in the day on Saturday,
potentially continuing overnight.

Convection continues on Sunday with a moisture remaining in
place. Without stronger synoptic forcing, scattered thunderstorm
development favoring the higher terrain is anticipated. As
guidance stands now, the potential for flash flooding remains
elevated over the burn scars, but lower than Saturday`s
potential.

Model guidance supports a decrease in moisture by the start of
the new work week, but with PWATs remaining above 100% of
normal, afternoon convection will likely continue over the
higher terrain each afternoon. An early look at temperatures
shows afternoon highs remaining 5-10 degrees above normal
through the seven-day forecast.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1142 PM MDT Thu Aug 20 2026

A few lingering showers are diminishing mostly in the Four
Corners area. Look for these to drop off over the next few
hours. Isolated showers and thunderstorms will pick up between
18Z and 00Z over the higher terrain along and south of the I-70
corridor with more scattered coverage across the Uintas in
northeastern Utah and the San Juans in southwestern Colorado.
Otherwise, expect VFR and light winds through the TAF period.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...None.
UT...None.

&&

$$

DISCUSSION...TGJT
AVIATION...DB