textproduct: Grand Junction

KEY MESSAGES

- This week will see daily afternoon thunderstorm chances, mainly on the higher terrain of western Colorado and eastern Utah.

- Localized heavy rainfall continues to pose a threat to flash flooding over burn scars and susceptible terrain.

- Daytime highs will run ~5 to 10 degrees above normal to start the week and will gradually increase through Friday.

DISCUSSION

Issued at 1023 AM MDT Tue Aug 25 2026

High pressure will continue to slide westward into the Desert Southwest through the end of the week. This will contribute to a gradual warming and slight drying trend, as the deeper plume of monsoonal moisture is shifted to the east. That said, surface moisture will linger under the high, with forecast PWAT values remaining 100-150% of normal through the end of the week. Limited dynamic forcing means that showers and thunderstorms will rely on orographic lift to form, resulting activity firing off the higher terrain each afternoon through the end of the week. Frequent lightning and gusty winds will be possible from any storms that form, along with localized heavy rain. Should storms form over a sensitive area, or train over the same area, flash flooding will be possible, along with debris flows associated with recent burn scars. As the high settles into the Southwest, temperatures will warm a degree or two each day. By the end of the week, highs will be 5-10 degrees above normal for late August.

A pattern shift will be possible late this week into the coming weekend, as a deep trough approaches the West Coast. Ahead of this trough, the tightening pressure gradient will lead to stronger winds. There is potential for at least localized Critical Fire Weather conditions, but that all depends on whether drier air is able to push in, or if wetter conditions will prevail. Guidance is in poor agreement at this time, as some deterministic and ensemble solutions favor wetter conditions, while others are running drier. It's something to stay tuned for. Troughing gradually overspreads the western CONUS through the weekend, introducing a wetter and cooler pattern. Current blended guidance is indicating temperatures near to a few degrees below normal as we move into early September.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1141 AM MDT Tue Aug 25 2026

Showers and thunderstorms will begin shortly and last through sunset. This convective activity will favor the high terrain. PROB30 has been included for the sites that are most likely to have impacts from storms. Primary concerns include lightning, gusty outflow winds around 25 kts, and brief periods of MVFR conditions from heavy rainfall. Otherwise, VFR conditions will prevail. Some sites could gust up to around 20 kts outside of convective activity, but winds will become light and terrain driven overnight.

GJT WATCHES/WARNINGS/ADVISORIES

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