textproduct: Grand Junction

KEY MESSAGES

- Multiple rounds of showers and storms are expected today, especially along and north of I-70.

- Another wet day is on tap tomorrow as well, with higher coverage of precipitation across southeast Utah and southwest Colorado.

- Flash flooding is possible through Monday evening as organized and training thunderstorms produce heavy rainfall over increasingly saturated soils, recent burn scars, and steep terrain.

DISCUSSION

Issued at 1146 AM MDT Sun Aug 30 2026

ELEVATED FLASH FLOODING THREAT THROUGH MONDAY:

Today's weather pattern is very similar to yesterday's with an upper- level jet draped along an axis from southwest Utah to central Wyoming. Locally, the jet will provide synoptic support for continued showers and storms along and north of I-70. The near- surface layer is more saturated today, so outflow winds will not be as impactful today. Stronger storms will be capable of producing 35- 45 mph gusts and frequent lightning.

With widespread precipitation expected in the same locations as yesterday, the threat for flash flooding will be higher today, especially in locations that receive multiple rounds of showers and storms. The same can be said for tomorrow, with flooding becoming more and more likely as soils and streams take on consecutive days of rainfall. Today, the potential for flash flooding will be along and north of I-70. Tomorrow, with richer moisture moving into the Four Corners region, the threat will primarily be along and south of I-70. Recent burn scars are especially susceptible to heavy rainfall which may cause debris flows and flash flooding regardless of location. Due to these reasons, a Flash Flood Watch is in effect for much of eastern Utah and western Colorado through Monday evening. Please see the Hydrology section below for more information.

LOOKING AHEAD:

A drier airmass moves in on Tuesday and remains in place for much of the work week. Afternoon showers and storms remain in the forecast over the higher terrain, but coverage will be much more isolated. Our first week of seasonable temperatures in quite some time will be the highlight of the week.

Ensemble guidance supports another push of monsoonal mositure across the Intermountain West next weekend. More details to come as the week progresses, but keep an eye on the forecast if you have outdoor plans next weekend.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1146 AM MDT Sun Aug 30 2026

Showers and isolated/scattered storms will continue to expand in areal coverage across wrn CO and ern UT TAF sites this afternoon and linger through the evening. Though current trends support the greatest areal coverage of showers/storms to be located across northern TAF sites into early Monday. PROB30 groups are in some TAF sites where storms are expected, and where gusty outflow winds and heavy rain will be the main concerns. Mainly VFR conditions will remain in place, with MVFR cigs and vsbys expected in stronger storms and showers, with brief IFR visbilities below 3 miles at times. Convection will continue into the overnight hours though the areal coverage of precipitation will diminish.

HYDROLOGY

Issued at 243 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. 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 Monday evening for COZ002-003-006>014- 017>021. Flood Watch from Monday morning through Monday evening for COZ022-023. UT...Flood Watch through Monday evening for UTZ022-025-027>029.