748
FXUS65 KGJT 021759
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1159 AM MDT Wed Jul 2 2025

.KEY MESSAGES...

- Showers and thunderstorms will once again form over the higher
  terrain this afternoon, with lightning and outflow winds
  capable of gusting in excess of 50 mph the primary concerns.

- With rich moisture in place and slow storm motions expected,
  heavy rain and localized flash flooding threats will be on the
  increase today and tomorrow.

- Near to below normal temperatures are expected through Friday,
  then a gradual warming and drying trend will last through the
  holiday weekend.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 306 AM MDT Wed Jul 2 2025

The closed low off the West Coast has moved on shore tonight, while
ridging continues to dominate much of the Intermountain West.
Between these two features, a tap of deep tropical moisture is
working into the Desert Southwest. This deep moisture has allowed
for clouds and a few light showers to linger well into the overnight
hours, helping keep temperatures mild. While the best of this
moisture is still to our west at the time of writing, as the West
Coast low tracks east today it will nudge the moisture plume more
directly into eastern Utah and western Colorado. As a result,
afternoon convection will be more widespread this afternoon, with an
increasing threat of heavy rainfall in addition to frequent
lightning and outflow winds capable of gusting 40-50 mph. Slow storm
motions and that increasing heavy rain threat will contribute to
create an isolated flash flooding threat this afternoon.
Additionally, the increased clouds and shower activity will limit
our high temperatures to near-normal values this afternoon.

It`s not unusual, with such rich moisture in place over the Western
Slope, to see convection linger well into the overnight hours. And
indeed, model guidance is picking up on this for tonight into
tomorrow morning, favoring areas around the Four Corners and
northward through eastern Utah. By Thursday morning, the open trough
will be approaching eastern Utah and western Colorado, nudging that
moisture plume eastward. Model guidance has PWATs running around
200% of normal by tomorrow afternoon. This moisture and the bit of
dynamic lift provided by the trough will certainly be enough to get
convection started, but the question becomes how much instability
will be present. That overnight convection mentioned earlier will be
the big concern, because lingering clouds could severely hamper the
development of daytime instability, and turn a widespread convective
event into a more stratiform type, with widespread steady rain and
embedded stronger storms. As high resolution guidance starts to come
in today, we will get a better handle on this. Regardless of the
form it takes, there is increasing confidence of a widespread
wetting rain event tomorrow, and an increasing concern of isolated
flash flooding in prone spots. Temperatures are expected to run 5-10
degrees below normal.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 306 AM MDT Wed Jul 2 2025

Showers and thunderstorms look to linger through the night Thursday
before tapering off early Friday morning. Models quickly diverge
from this point onward. While upper-level flow is fairly well agreed
upon between models on the 4th of July, moisture content widely
varies, with cluster analysis split evenly between above- and below-
normal QPF. Whatever moisture does persist will be mostly confined
to the northeastern portions of our CWA near the Park Range.
However, any amount of lingering moisture on the backside of the
departing trough may support scattered convection, particularly
along the high terrain, should orographics be favorable. It is
apparent that drier conditions resume heading into the weekend, but
consistency among models regarding the upper-level flow appears to
fall off greatly by this point. Ridging does seem to try and
reassert itself over the region through the weekend and into early
next week. Between this and the suggested drying trend, blended
guidance does want to gradually warm temperatures back to near or
slightly above normal values by the beginning of next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1154 AM MDT Wed Jul 2 2025

Another round of afternoon showers and thunderstorms will pose
some aviation challenges today and this evening for terminals.
Gusty outflow winds and ceilings will intermittently impact
airfields. Showers are expected to taper late evening, with
leftover clouds hanging around into the overnight hours. An
approaching frontal boundary will bring some more showers to the
region Thursday morning, likely producing lower ceilings near
breakpoint conditions for a few terminals.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...LTB
LONG TERM...BW
AVIATION...TGJT