textproduct: Grand Junction

KEY MESSAGES

- Strong to severe thunderstorms are possible along and north of I-70 Saturday, with damaging winds being the primary threat.

- Flash flooding is also possible Saturday as precipitation chances become more widespread ahead multiple rounds of showers.

- Storm chances remain in the forecast each afternoon through next week, as will the threat for flash flooding along vulnerable terrain.

- Cooler weather arrives with this current pattern. Daytime highs into next week could be hovering near or below normal.

DISCUSSION

Issued at 955 PM MDT Fri Aug 28 2026

COOLER AND WETTER WEEKEND:

A substantial pattern change is expected to take place Saturday as the high pressure previously centered over the Four Corners begins to break down as a result of an incoming trough to our northwest. During this transitional period, nocturnal convection is possible each night as moisture advection begins to intensify under dominant southwesterly flow aloft. As a result of this, eastern Utah and western Colorado will likely be waking each morning to cloud cover. This cloud cover will linger throughout the day, leaving us with widespread precipitation chances for the CWA this weekend. Additionally, PWATs are expected to surge to ~150-190% of normal. As far as temperatures are concerned, this weekend will see daytime highs within 5 degrees of normal, and they continue to be on the downward trend as we move towards next week.

SATURDAY:

Strong upper-level winds arriving Saturday will create enhanced wind shear along and north of I-70, setting the stage for a few strong to severe thunderstorms. Damaging wind gusts will be the primary threat with these storms. Gusts upwards of 60 mph were seen with some of Friday's storms. Therefore, cannot rule out a similar situation for Saturday, if not even higher gusts. Additionally, lightning, hail, and localized heavy downpours should not be ruled out. Flash flooding will also be a concern if storms slow down, stall, or repeatedly track over the same area.

SUNDAY:

Scattered to widespread thunderstorms will redevelop on Sunday, but as the upper-level jet dynamics depart to the northeast, the primary threat will shift from damaging wind to localized heavy rainfall. This inherently enhances the risk for flash flooding and debris flows on recent burn scars and susceptible terrain.

NEXT WEEK:

As we begin next week, ensembles are supporting PWATs >150% of normal through at least Monday, before a slight downturn in moisture for Tuesday and Wednesday. Although, models begin to diverge in outcomes by Wednesday leading to rather low forecast confidence midweek and beyond. All that being said, 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 /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 517 AM MDT Sat Aug 29 2026

A few showers, maybe a rumble of thunder, will continue this morning before more widespread convection starts forming. After 18Z, more widespread showers and storms will form with all TAF sites possibly seeing some convection on station. PROB30 groups will capture this possibility through much of the afternoon and evening hours. Under and near the stronger cells, gusty outflow winds and heavy rain will be the main concerns. Outside of convection, gusty winds of 20 to 25kts will be possible. Despite the convection, VFR conditions will remain in place though brief MVFR can't be ruled out as stronger storms and showers drop visbilities to below 3 miles.

GJT WATCHES/WARNINGS/ADVISORIES

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