textproduct: Grand Junction

KEY MESSAGES

- Scattered to widespread precipitation chances return Monday, with higher coverage of precipitation across southeast UT and southwest CO than previous days.

- Flash Flooding will continue to be possible as organized and training thunderstorms can produce heavy rainfall over a short period of time.

- Areas of concern for flash flooding will be those of increasingly saturated soils, recent burn scars, and steep terrain.

- Seasonable temperatures return for the first half of the week.

DISCUSSION

Issued at 934 PM MDT Sun Aug 30 2026

ELEVATED FLASH FLOODING THREAT THROUGH MONDAY EVENING:

A significant plume of moisture remains in place through at least Monday evening for much of the area. PWATs continue to hold steady at 160-180% of normal, with localized pockets of 200% of normal. This will mean another day of scattered to widespread showers and storms. Primary threats continue to be localized heavy rainfall, lightning, and gusty outflow winds (35-45 mph). This inherently means there is also a risk for flash flooding and debris flows along recent burn scars, susceptible terrain, and areas of increasingly saturated soils. As the richer moisture hovers around the Four Corners area, the flash flooding concern favors areas along and south of I-70 Monday. This will be especially true of areas that have received multiple rounds of precipitation over the past few days. For those reasons, a Flood Watch remains in effect for much of eastern Utah and western Colorado through Monday evening. See the hydrology section below for more information on that.

TUESDAY + BEYOND:

A drier airmass moves into the area by Tuesday and remains in place for much of the work week. Although afternoon showers and storms remain in the forecast over the higher terrain, but coverage will be much more isolated than previous days. A return to seasonable temperatures is also in the forecast for the first half of the week.

Models continue to be in agreement that another push of monsoonal moisture is on the horizon for the Intermountain West this coming weekend. But, that period still remains far out so the details are vague yet. Continue to monitor the forecast as changes are made.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 521 AM MDT Mon Aug 31 2026

Showers and thunderstorms will continue today with heavy rain, gusty winds and small hail all being a concern. TAF sites will all have chances to see this convection through the day so many PROB30 groups are in place to capture this possibility. Mainly VFR conditions will remain in place but MVFR, maybe brief IFR, will be possible as stronger storms and showers drop vis to below 3 miles. These showers and storms will continue past midnight before dissipating around 09Z.

HYDROLOGY

Issued at 934 PM MDT Sun Aug 30 2026

Anomalous moisture will remain locked across western Colorado and eastern Utah through the early part of the week. This is mostly driven by PWAT values holding at 160-180% of normal, with localized pockets of 200% of normal. Given the antecedent moisture from rainfall over previous days, soils in several sub-basins are already saturated, which could promote areas of rapid runoff and poor infiltration. A Flood Watch remains in effect through Monday evening for most locations.

The main threats remain flash flooding and debris flows, particularly over recent burn scars and susceptible terrain. Critical areas of concern within the Flood Watch include the Lee and Elk RX, Gold Mountain, Elk, Ferris, and Babylon burn scars, where hydrophobic soils have the ability to amplify peak flow under moderate rainfall rates.

Although drier air attempts to nudge into the region by Tuesday, lingering mid-level moisture and daytime heating will keep daily afternoon thunderstorms chances intact for the higher terrain regions. Hence, a localized flash flooding threat will remain beyond Monday for those areas.

GJT WATCHES/WARNINGS/ADVISORIES

CO...Flood Watch through this evening for COZ002-003-006>014- 017>021. Flood Watch through this evening for COZ022-023. UT...Flood Watch through this evening for UTZ022-025-027>029.