textproduct: Grand Junction

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 /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 1142 PM MDT Fri Jul 17 2026

Still have some light shower and isolated thunderstorm across northwest Colorado and southwest Colorado/southeast Utah with midlevel ceilings and a few gusts to 25 kts. Look for these storms to continue to diminish over the next few hours. Showers will develop over the higher terrain after 15Z with thunderstorm becoming dominant after 18Z. Convection will work down into the valleys through the afternoon, and begins to diminish after 00Z becoming more stratified showers after 03Z, much like this evening. The main threats with convection will be lightning, gusty outflows (30-40kts), and brief periods of MVFR in heavy rainfall.

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.