550
FXUS65 KGJT 301118
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
518 AM MDT Tue Sep 30 2025

.KEY MESSAGES...

- An approaching trough will result in increased cloud cover,
  along with some isolated mountain showers this afternoon, and
  scattered showers over northeast Utah this evening.

- Warmer and drier conditions return Wednesday through Friday,
  with temperatures climbing to 5-10 degrees above normal.

- A low pressure system moves through Saturday, bringing cooler
  and wetter conditions that will stick around into early next
  week.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 314 AM MDT Tue Sep 30 2025

High pressure continues to dominate across the eastern CONUS, while
low pressure rotates off the coast of the Pacific Northwest, with
troughing extending southward along the West Coast. A shortwave
rotating around this low pressure system is currently working
through the western Great Basin. Out ahead of this wave, a jet
streak aloft is pushing into the Four Corners region, bringing
increasing cloud cover along with it. Daytime mixing will tap into
the higher wind speeds associated with this jet streak, resulting in
breezy southwesterly winds with gusts of 25 to 35 mph this
afternoon. The southwesterly flow aloft is also expected to usher in
a slightly drier airmass. So while orographic showers are expected
to form on favored slopes early in the afternoon, the drier airmass
will limit coverage and shift the primary threat to gusty winds
rather than heavy rain. The shortwave trough moves in late this
afternoon, pushing the jet streak to the east and shifting the focus
for shower activity from the Colorado mountains to northeastern
Utah. There is some better moisture associated with the main trough,
but it`s also expected to be a fast moving feature. Chances for
precipitation over northeast Utah are expected to peak between 3PM
and 6PM, and then taper off into the evening. So while there will be
higher probabilities of wetting rain (up to 50%), the quick nature
of the system will limit actually precipitation totals to a tenth of
an inch or less. Skies gradually clear out Tuesday night, and
shortwave ridging builds in on Wednesday. Sunshine will dominate,
and temperatures will climb to 3-6 degrees above normal.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 314 AM MDT Tue Sep 30 2025

Ridging continues to build in across eastern Utah and western
Colorado through Friday morning, as the closed low off the Pacific
Northwest coast and its associated trough move inland. This will
resulting in a tightening pressure gradient aloft throughout the day
Thursday, resulting in potentially breezy southwesterly winds.
Temperatures will also gradually climb to 5-10 degrees above normal
through this period. By Friday morning, a cutoff low redevelops at
the base of the approaching trough over northeastern California and
northwestern Nevada, with an associated strong surface cold front.
Some model disagreement remains over the finer details of speed and
strength of this system, but overall guidance has come into some
semblance of consensus. The low is expected to swing into eastern
Utah and western Colorado on Saturday. Widespread precipitation,
with the potential for some light mountain snow, is expected, along
with much cooler temperatures. More substantial model disagreements
crop up Saturday night and beyond as guidance struggles to work out
the details of this messy, blocky pattern. However, looking at the
large scale picture, the western half of the country remains under
broad troughing which will keep conditions cooler and unsettled as
we move into early next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 515 AM MDT Tue Sep 30 2025

Mid level clouds have filled in over the last several hours,
with broken to overcast skies reported at most terminals. This
trend will continue through the morning, with KASE, KEGE, and
KRIL flirting with ILS breakpoints at times. Some fog has
developed around KGUC as well, which will linger through the
next few hours. Isolated afternoon showers or thunderstorms
will develop along the Colorado Divide, as well as across
northeast Utah. The main concerns with these showers are gusty
winds and lightning, and maybe some brief heavy rain.
Additionally, breezy southwesterly winds with gusts up to 25
knots are expected this afternoon. VFR conditions will prevail,
but drops to MVFR/IFR will be possible with stronger showers or
with isolated fog.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...BGB
LONG TERM...BGB
AVIATION...TGJT