textproduct: Grand Junction

KEY MESSAGES

- Showers and thunderstorms will continue each afternoon and evening through at least early next week.

- Main threats with these storms include lightning, localized heavy rainfall, and gusty outflow winds (35-45 mph).

- These storms have the ability to produce flash flooding and debris flows in vulnerable terrain, including areas near and downstream of burn scars.

DISCUSSION

Issued at 1004 PM MDT Sat Jul 18 2026

A few showers and thunderstorms are drifting southwestward in eastern UT this evening. This leftover convection will continue to decay. Stratiform storm debris will stick around in some fashion into the morning hours. This is only worth mentioning for its potential to temper convective initiation on Sunday morning. But...it's not if, but rather when will storms fire off again on Sunday. Little change in the air mass will spell out a rinse and repeat forecast Sunday afternoon. The high does amplify some, so afternoon highs look to trend up where cloud cover and showers don't impede heating. A few hot spots could get some cooling by evening given the likely outflows pinballing around the region. Generous CAPE on forecast soundings, along with rich PWAT values will ensure thunderstorms retain their ability to produce heavy rainfall rates, small hail, gusty winds, and the collateral impacts that come along, namely flash flooding. Storm motions will be similar to today, pushing east to west again Sunday afternoon.

With high pressure firmly entrenched over the West, temperatures will continue to trend a few degrees over average the first half of the work week. Daily showers and thunderstorms could keep hopes up for cooler evenings, especially where we can increase shower coverage on the mountains. Unfortunately, we are still waiting for better coverage of moisture to deliver on that promise. Model soundings do increase PWAT values Tuesday and Wednesday, as well as retain good forcing. A shift in the high's position looks inevitable too. This will shift storm motions and moisture transport sometime around Wednesday too. Models back off on temperatures mid week, stripping some of the triple digits out of the forecast. Deterministic models hint at the center of the high shifting east next weekend. Still too early in the game for that, but that will remain a pivotal forecast detail as the week wears on.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 1204 AM MDT Sun Jul 19 2026

A few showers and thunderstorms are pushing southwest through southeastern Utah that will move out of the region over the next few hours. Look for isolated showers and thunderstorms to develop over the higher terrain after 15Z becoming widely scattered after 18Z. Some storms will work down into the lower valleys through the afternoon, with storms diminishing after 00Z becoming more stratified showers after 03Z, much like this evening. The main threats with convection will be lightning, gusty outflows (30-40kts), and brief periods of MVFR in heavy rainfall. Otherwise, expect VFR conditions with light winds.

HYDROLOGY

Issued at 1012 AM MDT Sat Jul 18 2026

Anomalous moisture has become established across portions of eastern Utah and western Colorado. Rainfall rates of 1-2 inches per hour will be possible with the stronger storms. These rates could lead to flash flooding and debris flows especially over recent burn scars.

Storms over the last few days have helped prime lower levels of the atmosphere and saturate the ground where rain was observed. Several locations across southwest Colorado have reported 0.5 to 1.0 inches of rain within 30 minutes; which is more than sufficient to create issues in our steep, rocky terrain that is already susceptible to flash flooding. This environment also triggers heightened awareness over recent (or actively burning) fires, due to the burnt ground's inability of absorbing moisture under heavy rainfall. As such, we continue to emphasize the potential for flash flooding and debris flows in this regime.

As a reminder: Keep an eye on our forecasts through the end of the week and stay tuned for updated hydrology alerts if visiting or if you reside below vulnerable terrain to flash flooding and/or debris flows. Storms across the west develop quickly, leaving little room for lead time in flashy terrain.

GJT WATCHES/WARNINGS/ADVISORIES

CO...None. UT...None.