textproduct: Grand Junction

KEY MESSAGES

- Strong to Severe thunderstorms remain a threat this afternoon for northeast UT and northwest CO, including small hail and strong winds.

- Flash flooding remains a threat today through Monday as organized and training thunderstorms produce saturated soil conditions and excessive runoff.

- Cooler Temperatures arrive across the region this week.

- A downturn in moisture develops Tuesday, but concern for additional rainfall associated with extra-tropical moisture returns Wednesday.

DISCUSSION

Issued at 1132 AM MDT Sat Aug 29 2026

A plume of Pacific moisture ahead of a trough swinging through the Great Basin continues to produce scattered showers and thunderstorms. Thus far this morning, showers have managed to produce some gusts to around 40 mph. Storm motions remain swift, and thus the flash flooding risk remains low. Successive storms training across sensitive terrain this afternoon and this evening could quickly turn attention to flash flooding. Strong winds remain a threat as well, along with small hail, favoring northeast UT and northwest CO.

With a strong jet streak overhead Saturday night and early Sunday, showers and storms will likely be able to sustain themselves. High resolution models are preferring to keep this threat confined along the Continental Divide and across northeast UT and northwest CO. Showers and storms will taper early Sunday morning. Convective debris and cloud cover will likely provide some inertia to overcome Sunday as we see another round of convection develop ahead of another pinched off trough over the Great Basin. Ample moisture awaits, as WPC expanded their area of 15 percent risk of rainfall exceeding flash flood guidance over the entire CWA on Sunday. Storm motions still look brisk on Sunday, but increased training and coverage are likely to enhance the flash flood risk, yet again. Wetter boundary layers are expected to suppress some of the gustier outflow winds on Sunday. However, storms should still be capable of producing some 35-45 mph gusts, given the stronger winds aloft. The overhead jet streak doesn't yield much Sunday night and models are eager to keep some showers going into the early hours of Monday, likely tapering around daybreak.

NEXT WEEK:

As we begin next week, ensembles are supporting PWATs 160-180 percent of normal through at least Monday, before a slight downturn in moisture for Tuesday. Excessive rain outlooks from WPC have highlighted a 25 percent chance for rainfall exceeding flash flood guidance for much of eastern UT and western CO on Monday. While it's still too early to pinpoint flash flood coverage, flood prone areas across the region are highlighted in this heavy rainfall outlook. Models begin to diverge in outcomes by Wednesday leading to rather low forecast confidence midweek and beyond. There still remains a signal for another push of monsoonal moisture late next week. This moisture could also be enhanced by a tropical system situated in the eastern Pacific, which we will have to see evolve to gain a clearer picture. As for temperatures, a welcome relief is in store as daytime highs are expected to fall below normal to start next week.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1132 AM MDT Sat Aug 29 2026

Showers and isolated/scattered storms early, will continue to expand in areal coverage across wrn CO and ern UT TAF sites this afternoon and linger through the evening. PROB30 groups will continue at some TAF sites where storms are expected, where gusty outflow winds and heavy rain will be the main concerns. Despite convection, mainly VFR conditions will remain in place, with MVFR cigs and vsbys expected in stronger storms and showers, with brief IFR visbilities below 3 miles at times.

GJT WATCHES/WARNINGS/ADVISORIES

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