619
FXUS65 KGJT 232353
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
553 PM MDT Sat Aug 23 2025

.KEY MESSAGES...

- Scattered showers and thunderstorms are expected throughout
  this afternoon, mostly along the high terrain Gusty winds,
  frequent lightning, and moderate to heavy rain are all
  possible.

- Moisture continues to increase over the next several days,
  with widespread shower and storm activity expected. Potential
  for heavy rain and debris flows over burn scars will be
  heightened from Sunday into early next week.

- Temperatures are trending downwards, with near-normal highs
  expected tomorrow and well below normal highs throughout the
  work week.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 341 PM MDT Sat Aug 23 2025

Moisture continues its upward trend as a plume of anomalously
high PWAT`s continues to rotate around the Desert Southwest high
into the Intermountain West. As of the 18Z Grand Junction
sounding, PWAT`s have risen to just short of an inch.
Thunderstorms have gotten going already along the San Juans and
the Uncompahgre Plateau, but with some relatively deep CIN still
hampering convection, most storms to this point have been mild
and short-lived. This CIN should continue to erode over the
afternoon, though we should still see most storm development
remain along the high terrain. Should we be able to break that
cap, particularly over southwestern Colorado where mesoanalysis
suggests CAPE is exceeding 1000 J/kg, it`s possible that we
could have a few small hail-producing storms alongside the
strong 40+ mph outflows we`ve already seen occur today. Flash
flooding will continue to be a concern going forward as well,
particularly over burn scars and known flashy areas. Stay
weather- aware, especially if you plan on being outdoors.

The aforementioned plume of moisture spills back into the CWA
tomorrow as the Desert Southwest high migrates southeastwards
and flow turns more westerly. Ensembles are hinting at PWAT`s
surpassing an inch across most portions along the CO-UT border
during the afternoon, roughly 170-190% of normal. This should
transition us into a pattern of more widespread storm coverage,
not just on Sunday, but throughout much of the week. With the
push of moisture just getting going, morning cloud cover looks
to be scattered across much of the region. Models are keying in
on this being enough to bump the CAPE up quite a bit,
particularly in west-central Colorado along the I-70 and US-50
corridors. The more conservative models are still exceeding 500
J/kg, with more eager models reaching 1000 to 1500 J/kg.
According to deterministic models, this pairs with the
expectation for a weak shortwave to cross through the CWA in the
afternoon. This results in a fairly favorable setup for more of
a convective storm mode south of I-70, evident in CAM`s.
Morning cloud cover may be a little more stubborn north of I-70
though, and CAM`s are leaning towards more stratiform-type
showers tomorrow afternoon. As far as timing goes, some weaker
showers may form early in the morning, with stronger storms
developing around noon and persisting into the evening, possibly
well beyond sunset. Look for high temperatures to really begin
turning downwards at this point as well, with most of the region
returning to near-normal highs tomorrow.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Issued at 341 PM MDT Sat Aug 23 2025

High pressure remains in place for much of the week ahead, as
does monsoonal moisture. This weather pattern supports a cooler,
wetter week with daily precipitation chances and below normal
temperatures.

On Monday, the global ensembles support PWATs 150-185% of
normal area wide. Areas that see a little clearing in the
morning could see stronger convection develop in the afternoon,
but with the amount of moisture present it is more likely that
broken to overcast clouds will limit the amount of daytime
heating. This favors a transition to stratiform rains across
much of the region with some embedded storms here and there. If
this scenario does play out, the potential for burn scar flash
flooding will be low (10-30% chance).

Moisture advection strengthens Tuesday evening into Wednesday
which will keep stratiform precipitation chances elevated
through the overnight hours. Once again, we may see a decrease
in afternoon thunderstorm coverage in favor of a more stratiform
rain across much of eastern Utah and western Colorado.

Moisture begins to retreat to the north late Wednesday into
Thursday. Depending on the timing of this moisture retreat, we
could see a transition back to convective precipitation south of
I-70 on Thursday. If so, periods of moderate to heavy rainfall
and lightning chances will reenter the forecast.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 533 PM MDT Sat Aug 23 2025

Showers with embedded thunderstorms across eastern Utah and
southwestern Colorado will decrease through 06Z with lingering
isolated to scattered showers overnight in the southern
mountains. Isolated to scattered showers and thunderstorms will
increase again after 16Z along the I-70 corridor, becoming
widespread across the higher terrain of the region by 21Z. KTEX
and KDRO will see some impacts of low ceilings, reduced
visibilities, lightning and gusty winds this evening, but all
TAF sites will see these impacts after 18Z tomorrow.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...BW
LONG TERM...KAA
AVIATION...DB