textproduct: Grand Junction

KEY MESSAGES

- Afternoon showers and thunderstorms continue today and Wednesday, with a diminishing flash flooding risk.

- Gusty winds return Wednesday and Thursday, with afternoon gusts to around 35 mph for much of the region.

- A chance for additional monsoonal moisture arrives for the Labor Day weekend.

- Temperatures remain near normal this next week.

DISCUSSION

Issued at 1156 AM MDT Tue Sep 1 2026

Two synoptic scale features will continue to exert their influence on local weather this week. Cyclonic flow in the PACNW will allow some cooler air to moderate temperatures across the Great Basin, while a blocking ridge amplifies over the central Canadian provinces. This is all evolving beneath a jet streak that stretches from Baja across the Four Corners onto the Great Plains. While new moisture remains absent from the equation, remnant surface moisture from recent rainfall will get reworked today, and to a lesser extent Wednesday, to produce a few thunderstorms and showers. A few of these storms could sustain strong showers. A marginal risk for flash flooding continues this afternoon for flood prone areas, subject to heavy rainfall. As the previously mentioned jet begins to nose into northeast UT and northwest CO this evening, a few showers could get a lease on life into the overnight hours favoring areas north of I-70. While models remain ambivalent to overnight showers, it does appear that this jet streak overhead will keep some threat of light rain in the forecast into Wednesday morning.

Drier air approaches from the west on Wednesday, but some remnant moisture beneath the strong jet streak will get another chance to queue up some storms Wednesday afternoon. Strong steering winds will keep storm motions fast, thus reducing the flash flooding risk Wednesday. Gusty outflow winds will remain a threat. Those stronger winds aloft will mix down to the surface Wednesday afternoon with gusts to around 35 mph expected across the region. A few sheltered valleys will see lighter winds, but everywhere will feel breezier...perhaps another hint of autumn's arrival. Drier air continues to invade Thursday and winds remain breezy. Shower activity will taper Thursday, allowing for some reprieve in rainfall.

Holiday Weekend and Beyond

The deepening PACNW cyclone is projected to amplify high pressure over the central CONUS this weekend. As the high builds westward, models are hinting at another monsoonal fetch developing, potentially including some richer tropical storm moisture. This could send some heavy showers back into the Four Corners Friday and Saturday. Given the concern for flash flooding in the Southwest this time of year, weekend trekkers that are venturing into the slot canyons and onto the mountains will want to keep abreast of the forecast, given the increased chance for thunderstorms. Models attempt to eject the low across the Great Basin Monday. This could produce a wet Labor Day forecast to close out the weekend. This is a developing forecast and will command some attention as it evolves.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1141 AM MDT Tue Sep 1 2026

Isolated showers and thunderstorms have begun and will persist through the evening. PROB30 has been included for sites that are most likely to see this activity. Primary concerns are lightning and strong outflow winds. Brief periods of heavy rain are possible from stronger showers or thunderstorms. Winds will generally become light overnight.

GJT WATCHES/WARNINGS/ADVISORIES

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