201
FXUS65 KGJT 181202
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
602 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 1005 PM MDT Fri Jul 17 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 majority of these storms will initialize over
the higher terrain before spreading through the valleys as outflows
develop. Additional development is also possible where these
outflows collide with each other and the higher terrain, leading to
pop up thunderstorms. 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.

QUICK NOTE ON TEMPERATURES + NEXT WEEK:

As for daytime highs during this time period, we have increased
cloud cover to thank for temperatures near normal for the
foreseeable future for much of the region. Next week`s convection
looks to follow similar patterns as this week. Although, there may
be slight variations in where the storms materialize and drift off
the terrain. As HiRes guidance becomes available for that time
period, we may gain a better grasp on the "when and where".

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 557 AM MDT Sat Jul 18 2026

Showers will develop over the higher terrain favoring the
southern mountains after 15Z with thunderstorm becoming
predominant after 18Z. Convection will work down into the
valleys through the afternoon, and begins to diminish after 00Z
becoming more stratified showers after 03Z. The main threats
with convection will be lightning, gusty outflow winds
(30-40kts), and brief periods of MVFR in heavy rainfall.
Otherwise, expect VFR conditions with light winds across the
region.

&&

.HYDROLOGY...
Issued at 1047 AM MDT Fri Jul 17 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 reported over 0.5
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...BS
AVIATION...DB
HYDROLOGY...ERW