textproduct: Grand Junction

KEY MESSAGES

- Daily afternoon thunderstorm chances through the end of the week, 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 through Friday, then cool through next week.

- A pattern shift this weekend also brings wetter conditions Saturday and beyond.

DISCUSSION

Issued at 1038 PM MDT Wed Aug 26 2026

High pressure is centered over the S.Rockies and amplified across the Canadian Prairies to the Arctic...being squeezed between deeper upstream and downstream troughs. There is also a tropical system in the SE Pacific that will be feeding moisture into the ring of fire around the high. This keeps the highest PWAT upstream of us to end the week then feed the better forcing as we head into the weekend as the upstream trough begins to break down the Rockies ridge. Dynamic trop fields show a weak wave moving through the CWA overnight which will at least keep some clouds if not very isolated showers around through sunrise. This leaves us under weak forcing again for tomorrow afternoon and mainly terrain forced convection expected similar to today. Drier low layers will favor gusty outflow winds more than heavy rainfall but the right storm over a recent burn scar could still cause some issues. Friday will again be similar however the winds look be picking up a bit as the upstream trough moves farther inland and begins to impinge upon the ridge and tighten the SW gradient aloft. HDWI shows a weak signal over parts of eastern Utah into NW Colorado leading to localized areas of critical fire weather. Temperatures during this time remain above normal.

The northeast Pacific remains an active upstream impact to the pattern shift Saturday and beyond. A deeper pool of cooler, wetter air arrives Saturday. This, dare I say, looks more fall- like given the erosion of the monsoonal high pressure pattern. I'm sure we still have some warm days ahead of us, but this next week looks cooler and wetter. Tropical storm activity in the eastern Pacific could play into local moisture supplies later next week. This plays into September climatology and could supply some needed moisture to the West Slope...fingers crossed.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 522 AM MDT Thu Aug 27 2026

A few clouds continue to drift overhead this morning, posing no aviation concerns. Convection will begin after 18Z over the higher terrain with isolated shower and storms expected. KTEX may see a quick storm this afternoon so included them in PROB30 group. Not confident any other airfields will see convection on station. An occasional gusty wind of 20 to 25 kts will be possible this afternoon.

GJT WATCHES/WARNINGS/ADVISORIES

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