textproduct: Grand Junction

KEY MESSAGES

- Deep moisture continues through the weekend as remnants of tropical system Rachel move through the region, especially overnight and through Sunday. Rainfall totals of 2-3 inches are possible over the eastern Utah mountains and 1-2 inches across the San Juans with locally higher possible. Moderate to heavy rainfall rates are possible and smaller drainages and arroyos will be susceptible to excess runoff. Burn scars will also be under threat of debris flows.

- Strong thunderstorms are possible Sunday afternoon with gusty outflow winds the main threat. A few more organized storms could contain some hail and bring a flash flood threat with locally heavier rainfall rates, especially if training occurs.

- Expect strong winds 30 to 40 mph with gusts 40 to 50 mph Sunday with higher gusts over the higher terrain, especially over southeast Utah and portions of southwest Colorado where a Wind Advisory is in effect. - Another pattern change is possible by the middle of next week with an early season winter storm. Snow accumulation is possible above 10,000 ft with snow possible down to 8,000 ft. Forecast confidence is low at this time.

DISCUSSION

Issued at 1120 PM MDT Sat Oct 10 2026

The cutoff low off the Southern California Coast is picking up the remnants of Rachel as it ejects to the northeast in the southwesterly flow driven by the ridging over texas and the trough digging into the Great Basin. The showers and thunderstorms this afternoon have stratified out to light rain across eastern Utah and Western Colorado. Satellite imagery shows jet winds aloft running 80 to 100 kts at H250, more in line with the Euro model. The 00Z soundings showed deep moisture across northern Arizona extending to the northeast into Western Colorado. Models are in good agreement with the Pacific Northwest low continuing to descend south through the Great Basin Monday night before ejecting to the northeast across the region Tuesday into Wednesday. This pattern brings continued rain across much of the region tomorrow into Monday. Guidance is keeping the heaviest precipitation over the Uintas and Tavaputs at two to three inches and one to two inches over the terrain to the south and east with the lower valleys only seeing another quarter inch or so. The most significant weather will be the stronger winds across the region tomorrow afternoon and evening across the south with winds continuing through the overnight in the northern areas. A wind advisory is in effect for the Four Corners area and in the Moab area for winds 25 to 35 mph gusting to 50 mph. Elsewhere, look for windy conditions gusting to 35-40 mph in the lower valleys and 40-50 mph over the higher terrain. Though these winds will taper off in the late evening down south, they will pick up across the northern areas through the evening before tapering off in the overnight. There is uncertainty as to whether the skies will clear out in the morning to allow heating for stronger thunderstorms through the day, or remain cloudy to limit the stronger thunderstorms. With the strong flow aloft, any convection will be capable of mix the upper level winds down to the surface producing locally strong winds in excess of 60 mph.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 1146 PM MDT Sat Oct 10 2026

Breakpoint conditions are expected to persist through much of this TAF period as extra-tropical moisture streams through the region, bringing periods of thunderstorms, strong wind, and periods of heavy rain. Some brief windows of VFR conditions could open up Sunday as drier air intrudes from the southwest. Unfortunately, this will be met with a likely stronger convective environment, potentially triggering some strong to severe thunderstorms capable of producing damaging winds, hail, and heavy downpours. In short, the aviation weather will be complicated for much of this period. Strong winds are expected across the region as a jet max sets up overhead Sunday. This will also bring LLWS to many terminals. Conditions start improving some towards early Monday morning from eastern UT into western CO.

HYDROLOGY

Issued at 1152 AM MDT Sat Oct 10 2026

A strong low pressure system off the Pacific Coast will begin to draw in tropical moisture associated with Tropical Storm Rachel this weekend. This strong southerly fetch will draw anomalously high moisture content across the Desert Southwest and into eastern Utah and western Colorado. The chance for widespread precipitation increases this evening into Sunday. Total precipitation forecasts range from 1 to 3 inches across high terrain, with highest amounts favoring the Uintas, Tavaputs and the Southwest San Juan mountains.

Stronger thunderstorms are also possible Sunday afternoon, increasing the threat for flash flooding across vulnerable terrain. While confidence in location and rainfall rates remain low at this time, the potential for rapidly rising rivers, streams, normally dry arroyos and slot canyons are possible Sunday through Monday.

Please follow the evolving forecast, especially if your plans including recreating or commuting across eastern Utah and western Colorado Sunday onward. Also, keep in mind weather potential above your location and upstream, particularly for those who reside below sensitive terrain like recent burn scars.

GJT WATCHES/WARNINGS/ADVISORIES

CO...Wind Advisory from 9 AM Sunday to midnight MDT Sunday night for COZ020-021. UT...Wind Advisory from 9 AM Sunday to midnight MDT Sunday night for UTZ022-027-029.