textproduct: Grand Junction

KEY MESSAGES

- Moisture increases this weekend as remnants of tropical system Rachel move through the region, especially this evening through Sunday. Rainfall totals of 1-2 inches and locally higher are possible over the eastern Utah mountains and the San Juans. 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 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 1152 AM MDT Sat Oct 10 2026

DEEP MOISTURE INCREASES THIS WEEKEND:

Scattered showers are tracking across the area this morning with some isolated thunderstorm activity although rain rates remain light with gusty outflow winds underneath these showers. Tropical Storm Rachel is currently off the Baja coast and is anticipated to track inland across SoCal through western Arizona and into western Utah by Sunday. Deeper moisture from the remnants of this tropical system is expected to move across the area from the southwest this evening and overnight into Sunday with more widespread showers and embedded thunderstorms. This moisture is being pulled into a low pressure trough over the Pacific Northwest that will dive southward and deepen over the Great Basin, with a robust jet setting up across Utah. PWAT anomalies are expected to climb above 250 percent of normal this evening and peak near 300 percent of normal through Sunday. The details remain a challenge with the forecast as given this abundant moisture this evening and overnight, we could see more cloud cover which could inhibit convective potential and result in more of a steady light to moderate rainfall overnight into Sunday morning.

STRONG TO SEVERE STORMS POSSIBLE SUNDAY:

How much clearing occurs Sunday morning and afternoon remains to be seen but models are hinting at a bit of a dry slot working in across the Four Corners which could result in some areas of clearing and more sunshine to act on the deep moisture and instability in place. If this happens, more robust convection looks possible, especially across eastern Utah and far western Colorado. Given the proximity of the low from the remnants of Tropical Storm Rachel, strong gradient winds are expected as well as stronger shear upwards of 40 to 50 kts. CAPE is fairly modest around 500 J/kg across southeast Utah especially, so with more sunshine, we could see stronger storms develop Sunday afternoon and evening along this moisture gradient. Some could potentially be severe as well and it appears like the primary threat would be outflow winds. Hail is still possible as well given the shear but it looks like more speed shear than directional which would tend to result in more of a strong wind threat. With the deep moisture in place, any storms would be capable of locally heavier rainfall rates, which would cause concern for flash flooding but it's hard to pinpoint exactly where this threat is the greatest and it will be dependent on storm mode. All in all, the eastern Uintas are still forecasted to see the higher rainfall totals of 1 to 3 inches through Monday morning with the San Juans and Abajos seeing over an inch of rainfall but this may be more gradual over the course of the next 48 hours. Localized flash flooding is possible though with any stronger convection but storm motion will be fairly swift. Given those factors, confidence remains too low at this time for a flood watch.

STRONG WINDS EXPECTED SUNDAY:

In addition to the storm potential, the gradient winds increase with better mixing possible Sunday afternoon and evening if this clearing pans out. Forecasted winds across southeast Utah and portions of southwest Colorado are already expected to gust 40 to 50 mph, so issued a Wind Advisory from 9 am Sunday through midnight Sunday night for those areas. Convection would enhance those gusts where some locally higher gusts exceeding 55 mph are possible if stronger convection develops.

LOOKING AHEAD NEXT WEEK:

Things will taper off a bit on Monday as moisture decreases and instability decreases but a 100 kt jet remains in place so breezy conditions and decent shear could lead to some stronger storms still possible during the afternoon. The next system to impact the region is an early season winter storm as the cold- core Pacific Northwest low drops down through the Great Basin before lifting to the northeast across the region Tuesday evening and Wednesday. This won't bring a lot of snow to the region, but we will likely see some winter driving conditions on the mountain passes with low visibilities and periods of slick roads. We will likely see snow down to 8,000 ft, but don't expect any accumulation below about 10,000 ft. Stay tuned for updates on this one too.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1152 AM MDT Sat Oct 10 2026

Scattered showers and isolated thunderstorms will move across the region today. Ceilings will fill in at the mid levels and showers will become more widespread by the evening, with some embedded thunderstorms expected. Breakpoint conditions are likely to develop in and around showers. Winds pick up this afternoon and will gust to around 25-30 knots, with some stronger gusts possible around showers. Breakpoint ceilings become more probable as the TAF period wears on, and will continue through the TAF period and beyond.

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.