725
FXUS65 KGJT 181724
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1124 AM MDT Sat Jul 18 2026

.KEY MESSAGES...

- Showers and thunderstorms will continue each afternoon and
  evening through at least early next week.

- Main threats with these storms include lightning, localized
  heavy rainfall, and gusty outflow winds (35-45 mph).

- These storms have the ability to produce flash flooding and
  debris flows in vulnerable terrain, including areas near and
  downstream of burn scars.

&&

.DISCUSSION...
Issued at 1012 AM MDT Sat Jul 18 2026

The current upper level pattern is characterized by a stagnant high
pressure system. This will lead to many rinse and repeat days when
it comes to the forecast. Current guidance continues to suggest PWAT
values around 150-200% of normal for the next few days. This will be
enough moisture to support daily showers and thunderstorms each
afternoon and evening through the weekend for the CWA. It is also
becoming more possible that we hold onto this moisture into early
next week as well. A system moving along the US/Canada border will
cause the high to pivot allowing moisture to fill in across the
northern CWA, which has been relatively quiet. By mid next week the
flow shifts to more a more southerly and possibly westerly
direction. The will change the evolution of afternoon convection
compared to the last several days.

A majority of these daily storms will initialize over the higher
terrain before spreading through the valleys as outflows develop.
Additional storm development is also possible where these outflows
collide with each other and the higher terrain. The primary threats
with these storms include lightning and heavy rain, in addition to
small hail and gusty outflow winds (35-45 mph). Although we welcome
much of this rainfall with open arms, localized heavy rainfall could
result in flash flooding and debris flows. This is especially of
concern over highly sensitive areas like recent burn scars. The
hydrology section below discusses the risk in greater detail.

As previously mentioned, these storms have the ability to pop up
rather quickly, so be sure to monitor the forecast and have multiple
ways to receive weather alerts. This is especially important if you
are visiting or reside below terrain that is vulnerable to flash
flooding.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1012 AM MDT Sat Jul 18 2026

VFR cigs and vsby are expected to remain across most of western CO
and eastern UT TAF sites through the forecast period, except periods
of MVFR cigs/IFR vsby in and around thunderstorms. Showers and
isolated storms will continue to expand in areal coverage thru the
aftn. Convection today, is expected to diminish in a similar fashion
to yesterday, trending more twd stratified showers btwn 02Z and 04z.
The main threats with convection will be lightning, gusty outflow
winds (30-45kts), and brief periods of heavy rainfall.

&&

.HYDROLOGY...
Issued at 1012 AM MDT Sat Jul 18 2026

Anomalous moisture has become established across portions of
eastern Utah and western Colorado. Rainfall rates of 1-2 inches
per hour will be possible with the stronger storms. These rates
could lead to flash flooding and debris flows especially over
recent burn scars.

Storms over the last few days have helped prime lower levels of
the atmosphere and saturate the ground where rain was observed.
Several locations across southwest Colorado have reported 0.5
to 1.0 inches of rain within 30 minutes; which is more than
sufficient to create issues in our steep, rocky terrain that is
already susceptible to flash flooding. This environment also
triggers heightened awareness over recent (or actively burning)
fires, due to the burnt ground`s inability of absorbing moisture
under heavy rainfall. As such, we continue to emphasize the
potential for flash flooding and debris flows in this regime.

As a reminder: Keep an eye on our forecasts through the end of
the week and stay tuned for updated hydrology alerts if
visiting or if you reside below vulnerable terrain to flash
flooding and/or debris flows. Storms across the west develop
quickly, leaving little room for lead time in flashy terrain.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

DISCUSSION...TGJT
AVIATION...TGJT
HYDROLOGY...TGJT