textproduct: Grand Junction

KEY MESSAGES

- Showers and storms will continue this week each afternoon and evening, with coverage becoming more widespread by Tuesday and Wednesday.

- Primary threats include heavy rainfall, lightning, and outflow winds (30-40 mph). Some small hail will also be possible.

- 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 1102 AM MDT Mon Jul 20 2026

A stagnant high-pressure system remains parked over the area. This is leading to many rinse and repeat days when it comes to the current forecast. Shower and thunderstorm chances remain each afternoon and evening, at least for the first half of the week. Shower activity appears to become more widespread by Tuesday and Wednesday as a shortwave rotates around the high causing it to move to our southeast. This will allow PWATs to increase to upwards of 200% of normal. Primary threats continue to be heavy rainfall, lightning, and gusty outflow winds (35-45 mph). Small hail is also a possibility. With that being said, depending on where these storms choose to materialize, they introduce a threat for flash flooding and debris flows. This remains a concern for areas with vulnerable terrain, including recent burn scars in addition to burn scars from previous years. For greater detail on the flash flooding risk, see the hydrology section below.

By midweek, the high-pressure system will shift slightly, altering our storm tracks. While storms have recently been taking an unusual east-to-west path, the new pattern will likely steer them up from the south and perhaps the west by late week. After that shortwave passes to our north westerly flow becomes established. This may alter the moisture across the area, which in turn may change daily storm chances.

As far as temperatures are concerned, daytime highs will continue to be above normal for the next few days, with near normal temperatures expected Wednesday and beyond.

A special note for outdoor enthusiasts: Please continue to monitor the forecast and adjust your plans as needed. These storms can develop rapidly, bringing sudden hazards. Your best bet is to head out early in the morning, as storm activity typically strengthens in the afternoon. Always ensure you have multiple ways to receive weather warnings.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1148 AM MDT Mon Jul 20 2026

Isolated showers and thunderstorms will develop today, mostly over the higher terrain at first, then moving into some valley areas. The primary concerns are strong outflow winds, lightning, and heavy rainfall. Periods of heavy rainfall could cause brief MVFR conditions. Otherwise, VFR conditions will prevail. Showers and thunderstorms are expected to persist through the late evening.

HYDROLOGY

Issued at 1102 AM MDT Mon Jul 20 2026

Anomalous moisture has become established across portions of eastern Utah and western Colorado. Scattered thunderstorms capable of producing heavy rain are expected this afternoon and early evening. 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 steep terrain and recent burn scars. Also, rain over the past several days has lead to saturated soils, which increase the chances for excessive runoff.

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.