textproduct: Grand Junction

KEY MESSAGES

- Scattered storms capable of producing gusty outflow winds and lightning will develop over the high terrain on today.

- Thunderstorm coverage increases this weekend with monsoonal moisture moving in. Flash flooding will be possible, especially Saturday.

- Temperatures remain 5-10 degrees above normal through the seven-day forecast, with today looking to be the warmest day.

DISCUSSION

Issued at 1149 AM MDT Fri Aug 21 2026

HOT WITH MOUNTAIN STORMS TODAY:

High pressure centered directly over our region will keep high temperatures hot today, with highs around 10 to 15 degrees above normal expected. The center of high pressure will gradually shift to our southeast, eventually shifting flow over our area to more southwesterly, which will support stronger moisture advection into our region. Today showers and thunderstorms will favor the high terrain, with the greatest chances and expected rainfall amounts favoring the southern Colorado mountains. The primary concerns with showers and thunderstorms today are gusty outflow winds up to 35 mph, lightning, and periods of heavier rainfall. Heavier rainfall could cause localized flash flooding over burn scars and susceptible terrain.

COOLER WITH WET WEATHER THIS WEEKEND:

Southwesterly flow will allow for moisture to increase across our region this weekend, with PWATs peaking around 150% of normal. This will lead to more widespread precipitation chances. Storms are still expected to favor the high terrain areas, but valley areas could see a few storms as they move off of the terrain. A shortwave moving through will provide additional lift while atmospheric moisture is elevated on Saturday, meaning stronger thunderstorms with heavier rainfall are possible, which subsequently increases flash flooding and debris flow concerns.

Convection continues on Sunday while the increased atmospheric moisture remains in place, but PoPs decrease and more strongly favor the high terrain as no additional lift from synoptic forcing is expected. Flash flooding concerns over burn scars and susceptible terrain persists through at least Sunday. Moisture looks to decrease but still remain above normal after Sunday, which will keep afternoon mountain showers and thunderstorms in the forecast daily.

High temperatures cool by about 5 degrees between today and Saturday. Despite the drop in temperatures, highs will still be around 5 to 10 degrees above normal for this time of the year. Highs will remain around 5 to 10 degrees above normal through early next week.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1149 AM MDT Fri Aug 21 2026

Isolated showers and thunderstorms will develop over the higher terrain this afternoon, with more scattered coverage across the Uintas in northeastern Utah and the San Juans in southwestern Colorado. Mid-level clouds will increase from the west after 06Z in eastern Utah ahead of a monsoonal push into the region. Otherwise, expect VFR and light winds through the TAF period.

GJT WATCHES/WARNINGS/ADVISORIES

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