textproduct: Grand Junction

KEY MESSAGES

- Strong to severe thunderstorms are possible along and north of I-70 tomorrow with damaging wind being the primary threat. Flash flooding is also possible with multiple rounds of showers and storms on the table.

- Thunderstorms continue each afternoon through the seven-day forecast as monsoonal moisture ebbs and flows across the region, as will the threat for flash flooding. - Cooler weather arrives with this stormy pattern. After today, high temperatures are projected to be within 5 degrees of normal.

DISCUSSION

Issued at 1230 PM MDT Fri Aug 28 2026

HOT WITH SCATTERED SHOWERS AND STORMS TODAY:

High pressure remains centered south of the Four Corners with hot and predominately dry conditions continuing for one more day. Some remnant moisture remains trapped under the high which will result in scattered afternoon storms over the high terrain. Flash flooding cannot be ruled out under stronger storms, but the threat is very low and primarily contained to recent burn scars and susceptible terrain.

The pressure gradient will tighten a bit today as a low pressure system moves into the Pacific Northwest, allowing for breezy afternoon winds especially across northeast Utah and northwest Colorado. Gusty and erratic winds are also anticipated near thunderstorms this afternoon with a dry near-surface layer in place. As a result, an isolated severe storm or two cannot be ruled out with damaging wind being the primary concern.

COOLER AND WETTER THIS WEEKEND AND BEYOND:

A substantial pattern change arrives tonight as high pressure begins to break down with a broad trough approaching from the west. Nocturnal convection is likely as moisture advection intensifies within the southwesterly flow aloft. This will set most of eastern Utah and western Colorado up for a cloudy Saturday with chances for multiple rounds of showers and storms as PWATs surge to ~175% of normal. Most notably, a strong upper- level jet will provide enhanced shear along and north of I-70. This will support the potential for a few strong to severe storms with damaging wind gusts being the primary treat. Training thunderstorms will also be capable of producing flash flooding.

Strong storms develop again on Sunday, but with the jet departing to the northeast, flash flooding becomes the primary threat of strong and/or training thunderstorms.

Ensembles support PWATs of >150% of normal through Monday, before a slight downturn in moisture is likely for Tuesday and potentially Wednesday. Although an increase in model spread begins to lower forecast confidence by mid week, another solid push of monsoonal moisture moves into the Southwest later in the week. An eastern pacific tropical system is also possible next week, so we'll be watching the track of that system to see if we can potentially tap into that rich, tropical moisture later in the week. Stay tuned!

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1150 AM MDT Fri Aug 28 2026

Winds will increase this afternoon across the region with gusts 25 to 30 mph. Clouds will be on the increase with scattered to broken mid and upper level ceilings. This all arrives ahead of a system pumping moisture into the Southwest. Some stronger thunderstorms can be expected across northeast UT and northwest CO. Gusty outflow winds could gust to around 40 mph with a few storms this afternoon and this evening. Elsewhere, terrain based showers and thunderstorms can be expected with less widespread coverage. Breakpoint conditions could temporarily develop under thunderstorms, but are not expected until Saturday when more widespread shower activity lowers ceilings. Some overnight shower activity tonight is being proposed by models, but confidence in its coverage remains low.

GJT WATCHES/WARNINGS/ADVISORIES

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