textproduct: Grand Junction

KEY MESSAGES

- Dry conditions and near-normal temperatures this afternoon with an isolated mountain shower possible.

- A frontal boundary promises additional showers mainly over high terrain Tuesday and Wednesday with afternoon gusty winds.

- A warming trend will continue. Triple digits will remain confined to the Four Corners and low desert valleys.

- Monsoonal flow begins to appear in model outputs this weekend.

DISCUSSION

Issued at 1133 AM MDT Mon Aug 17 2026

Dry, southwesterly flow will begin to shift this afternoon into a more zonal regime, ahead of a ridge of high pressure developing over the Great Basin later this week. This will set up a weak frontal boundary Tuesday and Wednesday with a concentration of moisture across our northern counties. These westerly plumes tend to get chewed up crossing the Great Basin. We should get some cloud cover Tuesday and an uptick in shower activity on the Uintas and Flat Tops, as well as along the west edge of the Continental Divide. The amplifying ridge bumps the frontal boundary eastward Wednesday, while models try to resolve some moisture under the center of the high(located over western UT). It looks like shower and storm development becomes more centralized over the terrain of Colorado from the Flat Tops down to the San Juans Wednesday afternoon. Moisture remains rather vague, as it doesn't ever tap a true monsoonal plume.

Late week begins to embrace another pattern shift. Temperatures surge beneath the subsident high straddling the Four Corners. Triple digits become more widespread in the desert valleys and red rock of Utah. Ensembles begin to grapple with monsoonal moisture Thursday and beyond. Statistical spread remains high, cluing some uncertainty in the model outputs. For now, planning around an uptick in monsoonal thunderstorms after Thursday would be optimum. Model solutions point to strengthening moisture over the weekend, with the caveat of uncertainty in statistical spread. Given the showery, monsoonal regime over the region, temperatures take a return towards cooler, normal values this weekend.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1118 AM MDT Mon Aug 17 2026

Generally few to scattered cloud cover is expected today. An isolated shower cannot be ruled out, but no impacts are expected to any terminals. Winds will be on the milder side with gusts not expected to exceed 18 kts. VFR conditions persist throughout the TAF period.

GJT WATCHES/WARNINGS/ADVISORIES

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