textproduct: Grand Junction

KEY MESSAGES

- A frontal boundary promises additional showers mainly over high terrain Tuesday and Wednesday with gusty afternoon 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 1040 PM MDT Mon Aug 17 2026

High pressure is building into the southwest, with a ridge developing across the Great Basin. Flow aloft has turned zonal, and the expected moisture increase is evident in the form of increased cloud cover across northern Utah and Wyoming. A weak frontal boundary is accompanying this moisture, and will help to bring increased cloud cover and shower activity to northeast Utah and northwest Colorado, as well as along portions of the northern and central Divide Tuesday. This boundary will track southeast into Wednesday, bringing more activity to portions of the central and southern Divide. Dry surface levels and relatively modest PWATs (on the order of 100-140% of normal) will limit heavy rain potential the next few days. The most likely impacts from any showers or thunderstorms will be gusty, erratic outflow winds and frequent lightning. Outside of shower activity, look from some breezy afternoon winds, with gusts of 20-25 mph. Temperatures will run 5-10 degrees above normal.

High pressure remains centered around the Four Corners through the end of the week, keeping temperatures above normal and generally dry conditions. However, a pattern shift is looking to set up late week and into the weekend. A trough moves toward the West Coast late week, nudging the center of the high eastward. There's a signal for a return to monsoonal flow, as moisture-rich southerly to southwesterly flow sets up over the Desert Southwest. However, there remains quite a bit of spread over how much moisture will reach eastern Utah and western Colorado. This should become clearer with subsequent model runs. Increasing moisture will bring increased cloud cover and more showers and thunderstorms for the coming weekend, along with temperatures dropping back to near-normal values.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1124 PM MDT Mon Aug 17 2026

Isolated showers and thunderstorms brush the northeastern Utah ans northwest Colorado after 09Z. Thunderstorms become more scattered across the higher terrain along and north of I-70 after 18Z and diminish after 00Z with showers lingering along the northern divide through the overnight. Primary threats are outflow winds gusting to 40 kts and lightning. Otherwise, expect VFR conditions with light winds becoming westerly after 18Z gusting 15-25 kts and dropping off after about 02Z.

GJT WATCHES/WARNINGS/ADVISORIES

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