983
FXUS65 KGJT 190609
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1209 AM MDT Wed Aug 19 2026

.KEY MESSAGES...

- Showers and thunderstorms redevelop over the higher terrain Wednesday
  afternoon and evening. Main concerns will be gusty outflow
  winds and lightning.

- 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,
  along with cooler, more seasonal temperatures.

&&

.DISCUSSION...
Issued at 1026 PM MDT Tue Aug 18 2026

A frontal boundary is dropping south through eastern Utah and
western Colorado tonight into Wednesday, triggering some scattered
showers and thunderstorms. An accompanying upper level jet is
keeping this shower activity tracking along pretty quickly, and dry
surface levels are limiting the amount of precipitation reaching the
ground. The main concerns continue to be gusty outflow winds and
lightning. Showers and storms will taper off after midnight, but
will redevelop across the higher terrain Wednesday afternoon and
evening, again with the same concerns. The frontal boundary will
drift east by Thursday as ridging builds in across the Four Corners.
Enough moisture trapped under this ridge will keep chances for
mountain showers and thunderstorms in the forecast, but storm motion
will slow right down with the lack of steering flow. This means
that, while surface levels remain dry, a slow moving storm over a
sensitive area could eventually lead to some heavy rain and flash
flooding concerns. Otherwise, temperatures continue to rise through
the end of the work week, running around 10 degrees above normal by
Friday. Triple digit heat will be possible across the desert valleys
of eastern Utah and western Colorado.

An omega block sets up for the weekend, with the high centered just
far enough east of the Divide for southwesterly flow to dominate
over the Great Basin and Southwest. As a result, monsoonal moisture
will begin advecting into the region. Discrepancies on things like
timing, intensity, and extent of the moisture plume remain between
deterministic and ensemble model solutions. However, the overall
signal of above normal moisture returning to eastern Utah and
western Colorado remains, increasing forecast confidence. Clouds,
showers, and thunderstorms will become more widespread through the
weekend, along with a return to more seasonable temperatures.
Further speculation on impacts will depend on storm motion, the
potential for training storms, and instability resulting from cloud
cover (or the lack thereof), all of which are too early to speak on
with confidence at this time. We`ll have to wait on higher
resolution guidance and better model consensus before these details
become clearer.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1124 PM MDT Tue Aug 18 2026

A band of isolated to scattered showers with a few embedded
thunderstorms are quickly moving east across the region generally
along and north of I-70 favoring the higher terrain. Look for
these showers to to sag south to about KMTJ and KGUC through
the overnight as they diminish, ending by about 12Z. Isolated to
scattered showers and thunderstorms pick up again after 16Z
favoring the mountain areas. Primary threats are lightning and
outflow gusts to 35 kts. Probabilities remain low, 20%, at TAF
sites, but expect storms over the mountain around KEGE, KASE,
KTEX and KDRO through the afternoon. Conditions should remain
above ILS breakpoints. Otherwise look for VFR conditions with
light winds becoming westerly after 18Z with gusts 20-25 kts.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

DISCUSSION...BGB/TGJT
AVIATION...DB