579
FXUS65 KGJT 181146
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
546 AM MDT Tue Aug 18 2026

.KEY MESSAGES...

- A frontal boundary promises additional showers mainly over
  high terrain Tuesday and Wednesday with gusty afternoon
  winds.

- A warming trend will continue. Triple digits will remain
  confined to the Four Corners and low desert valleys.

- Monsoonal flow begins to appear in model outputs this weekend.

&&

.DISCUSSION...
Issued at 1040 PM MDT Mon Aug 17 2026

High pressure is building into the southwest, with a ridge
developing across the Great Basin. Flow aloft has turned zonal, and
the expected moisture increase is evident in the form of increased
cloud cover across northern Utah and Wyoming. A weak frontal
boundary is accompanying this moisture, and will help to bring
increased cloud cover and shower activity to northeast Utah and
northwest Colorado, as well as along portions of the northern and
central Divide Tuesday. This boundary will track southeast into
Wednesday, bringing more activity to portions of the central and
southern Divide. Dry surface levels and relatively modest PWATs (on
the order of 100-140% of normal) will limit heavy rain potential the
next few days. The most likely impacts from any showers or
thunderstorms will be gusty, erratic outflow winds and frequent
lightning. Outside of shower activity, look from some breezy
afternoon winds, with gusts of 20-25 mph. Temperatures will run 5-10
degrees above normal.

High pressure remains centered around the Four Corners through the
end of the week, keeping temperatures above normal and generally dry
conditions. However, a pattern shift is looking to set up late week
and into the weekend. A trough moves toward the West Coast late
week, nudging the center of the high eastward. There`s a signal for
a return to monsoonal flow, as moisture-rich southerly to
southwesterly flow sets up over the Desert Southwest. However, there
remains quite a bit of spread over how much moisture will reach
eastern Utah and western Colorado. This should become clearer with
subsequent model runs. Increasing moisture will bring increased
cloud cover and more showers and thunderstorms for the coming
weekend, along with temperatures dropping back to near-normal values.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 529 AM MDT Tue Aug 18 2026

Currently isolated showers are moving east across northeastern
Utah and northwest Colorado. Look for showers to become more
scattered with isolated thunderstorms by 18Z over the higher
terrain along and north of I-70, continuing through the
afternoon before diminish after 00Z with showers lingering
along the northern divide through the overnight. Primary threats
are outflow winds gusting to 40 kts and lightning. Otherwise,
expect VFR conditions with light winds becoming westerly after
18Z gusting 15-25 kts and dropping off after about 02Z.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

DISCUSSION...BGB
AVIATION...DB