textproduct: Grand Junction

KEY MESSAGES

- Warm overnight lows and triple digit highs for portions of eastern Utah and western Colorado are expected through Tuesday morning. The Heat Advisories remain in place.

- Afternoon and evening showers and storms will continue thanks to ample moisture and daytime heating.

- Slow storm motions will allow heavy rain under the stronger cells. Small hail and gusty outflow winds will also be possible.

- Watch out for flash flooding and debris flows in vulnerable terrain, especially for areas near and downstream of burn scars.

DISCUSSION

Issued at 1218 PM MDT Mon Jul 27 2026

High pressure centered to our southeast, and the resultant southwesterly flow over our area, continues to advect monsoonal moisture into our CWA. Storm motion is forecast to remain slow while ridging is aloft. At the same time, this mornings sounding shows that precipitable water remains well above normal for this time of the year, and there is an increase in instability when compared to yesterday. So, expect another day of slow moving storms capable of producing heavy rainfall. This means flooding and debris flow concerns remain elevated, especially over our recent burn scars. Lightning, small hail, and strong outflow winds are also concerns with thunderstorms.

Highs remain anywhere from 5 to 10 degrees above climatological norms with 100s still in the forecast for many lower elevations. Overnight lows will drop, obviously, but still remain above normal and without much relief, the going Heat Advisory remains in effect for the Grand Valley and Lower Yampa River Basin through tomorrow morning.

Looking ahead, a shortwave looks to move across the area Wednesday. If this should occur, thunderstorm chances will become more widespread, and potential for some stronger thunderstorms would increase. Keep an eye on the latest forecast. After that, high pressure continues to be forecast to build in to our west. Flow around the high will cause moisture to slowly decrease which will temper convection across the region.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 518 PM MDT Mon Jul 27 2026

Shower and storm chances will gradually diminish after 01-02Z at most terminals. Winds will return to light and terrain driven by the overnight hours. Cloud cover lightens overnight, with more development by Tuesday afternoon. Storm chances return by 18Z Tuesday for many of the high country terminals. Included PROB30 groups to account for that threat. Primary concerns with these storms continue to be lightning, localized heavy rainfall, and gusty outflow winds.

HYDROLOGY

Issued at 1218 PM MDT Mon Jul 27 2026

Scattered slow moving thunderstorms capable of producing heavy rainfall will develop each afternoon through at least midweek. Rainfall rates of 1-2" per hour will be possible, potentially even greater for brief periods of time with stronger storms. These rates could lead to flash flooding and debris flows, especially over steep terrain and recent burn scars. Saturated soils from consecutive days for rainfall will increase the potential for flash flooding as well.

As a reminder: Keep an eye on our forecasts and stay tuned for updated hydrology alerts if visiting or if you reside near terrain vulnerable to flash flooding and/or debris flows. Dry creeks and arroyos can fill quickly and without warning from storms miles away.

GJT WATCHES/WARNINGS/ADVISORIES

CO...Heat Advisory until 6 AM MDT Tuesday for COZ001-006. UT...Heat Advisory until 6 AM MDT Tuesday for UTZ022-024-027-029.