textproduct: Grand Junction

KEY MESSAGES

- Strong to Severe thunderstorms remain a threat this afternoon for northeast UT and northwest CO, including small hail and strong winds.

- Flash flooding remains a threat today through Monday as organized and training thunderstorms produce saturated soil conditions and excessive runoff.

- Cooler Temperatures arrive across the region this week.

- A downturn in moisture develops Tuesday, but concern for additional rainfall associated with extra-tropical moisture returns Wednesday.

UPDATE

Issued at 427 AM MDT Sun Aug 30 2026

Latest guidance continues to suggest rounds of showers and thunderstorms today and into the evening hours across the CWA. With increased monsoonal moisture, heavy rain will be a concern through the day along with gusty outflow winds and small hail. Recent burn scars are especially susceptible to heavy rainfall which may cause debris flows and flash flooding. Due to these reasons, went ahead and issued a Flood Watch to account for these possibilities.

DISCUSSION

Issued at 1131 PM MDT Sat Aug 29 2026

Models are in good agreement with a trough along the West Coast with the associated low tracking east along the Washington/BC Border and a broad high pressure over Texas pulling deep monsoonal moisture up through Arizona into eastern Utah and Western Colorado keeping pwats over an inch, and keeping the jet in place southwest to northeast across the Western States. Though most of the energy across the north was spent on the afternoon thunderstorms, upper-level dynamics are keeping showers in the forecast with occasional lightning overnight. The moisture stays in the area into Tuesday before drier air pushes in from the northwest.

The jet is dipping south across the region to support the convection we had Saturday across the northern areas spreading south of I-70 to the San Juans Sunday. A shortwave trough drops down Sunday afternoon into the evening bringing a round of stronger thunderstorms with nocturnal storms into Monday. A second shortwave is threatening a repeat Monday afternoon and evening, but models are diverging on the timing, so confidence is lower at this point. Stay tuned for updates. The primary threats are flash flooding due to heavy rain and training storms, especially near recent fire scars, possible large hail, and 60 mph outflow winds as is typical with severe thunderstorms. Though the air will be saturated to the surface, expect strong winds due to the wet downbursts mixing down the 40 mph flow at H500.

Models further diverge in outcomes by Wednesday leading to rather low forecast confidence midweek and beyond. There still remains a signal for another push of monsoonal moisture late next week. This moisture could also be enhanced by a tropical system situated in the eastern Pacific, which we will have to see evolve to gain a clearer picture. As for temperatures, a welcome relief is in store as daytime highs are expected to remain below normal through mid week.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 520 AM MDT Sun Aug 30 2026

Showers and storms continue this morning though there will be a break midmorning before another round of convection begins. Showers and storms are expected to affect all TAF sites in some form or fashion so many PROB30 groups are in effect for those showers and storms. ILS breakpoints will be reached today for many TAF sites as low cigs and vis though they aren't expected to be below them for prolonged periods. So too will brief MVFR/IFR occur thanks to showers drop cigs and vis. Convection will likely continue overnight though coverage will be much less.

GJT WATCHES/WARNINGS/ADVISORIES

CO...Flood Watch through this evening for COZ002-003-006>014- 017>021. UT...Flood Watch through this evening for UTZ022-025-027>029.