textproduct: Grand Junction

KEY MESSAGES

- Showers and thunderstorms redevelop over the higher terrain today and Thursday. Main concerns will be gusty outflow winds and lightning.

- Shower activity increases Friday and beyond.

- Triple digit temperatures begin to accumulate Thursday and Friday around the Four Corners and in the low desert valleys.

- Monsoonal flow could produce flash flooding this weekend, along with cooler, more seasonal temperatures.

DISCUSSION

Issued at 1226 PM MDT Wed Aug 19 2026

Weak shortwave energy continues to propagate across the region this morning. A sizable cumulus field has begun to sprout up on much of the terrain already. Showers and thunderstorms are possible on most of the mountains this afternoon. Storm motions will slide northwest to southeast. Dry valleys will likely inherit a few gusty outflows from decaying storms this afternoon, but little in the way of rainfall. Flash flooding is unlikely today. However, stronger showers on recent burn scars always warrant a watchful eye towards quickly changing conditions. Shower activity will wane this evening.

High pressure will continue to evolve over the Southwest Thursday, with little change from today's mountain shower regime. Temperatures will respond accordingly, ratcheting upward in excess of 10 degrees over climatology Thursday and Friday. Showers and clouds will play a role in potential for afternoon highs across the mountains. However, warm desert valleys will remain characteristically hot until they can tap into some moisture and cloud cover. Mountain showers will become more concentrated into Friday, especially on the San Juans, where additional moisture could increase the risk of flash flood concerns.

High pressure begins to shift eastward Saturday, introducing additional moisture and dynamic forcing at the hands of shortwave ripples in the mean flow. This is expected to produce another round of elevated flash flood potential. Models pull the high eastward Sunday. This is expected to shift moisture and forcing. However, additional showers should be expected Sunday afternoon and beyond, as models grapple with the downstream evolution of the high pressure over the Plains. Temperatures will continue to trend around normal for late August and afternoon showers continue on the mountains.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 544 PM MDT Wed Aug 19 2026

Isolated and scattered showers and thunderstorms have developed over the high terrain and will continue through sunset with a few drifting over lower elevations. Primary threats are lightning and gusty outflow wind gusts to 35 kts. Conditions should remain above ILS breakpoints with VFR conditions primarily with breezy afternoon winds with gusts 20 to 25 kts. Skies will clear overnight with light, terrain driven winds.

GJT WATCHES/WARNINGS/ADVISORIES

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