textproduct: Grand Junction

KEY MESSAGES

- Localized critical fire weather conditions continue today, becoming widespread under strong winds Saturday.

- The threat of terrain-based dry thunderstorms emerges today into the weekend, increasing the odds for new fire starts.

- Fire weather conditions become more localized Sunday, gradually increasing in coverage through early next week as hot and dry conditions return.

DISCUSSION

Issued at 934 PM MDT Thu Jun 18 2026

The ridge begins to break down today as troughing pushes in from the west. Flow aloft will gradually shift to westerly and then southwesterly by tonight. Ahead of this flow shift, a bit of upper level moisture tries to sneak in under the ridge. This moisture looks to be enough to fire off a few isolated showers or thunderstorms over the higher terrain, mainly favoring the San Juans and the Eastern Uintas. With such a dry surface layer in place, any showers or storms that do form will be far more likely to produce gusty and erratic outflow winds and dry lightning rather than any measurable precipitation. Another little push of moisture is forecast to sneak in with the trough passage Saturday and Sunday, this time favoring isolated convection over the northern ranges a bit more. But the same issues remain, dry surface air limiting the chances of any wetting rain and increasing the probability of dry lightning causing new fire starts. This trough will at least bring a break from the triple digit heat. After another day of 10+ degree above normal temperatures today, highs over the weekend will drop to near or around 5 degrees above normal. Unfortunately, high pressure builds back in over the Southwest early next week, and with its return so does the heat. Highs return to around 10 degrees above normal, and triple digits return to the desert valleys.

Saturday remains the next chance for widespread critical fire weather conditions, as southwesterly winds increase between the approaching troughing the weakening ridge. Winds will gust 30-40 mph across much of the region, with locally higher gusts possible. Dry surface levels remain stubbornly in place, with daytime minimum relative humidity values in the low teens to single digits for all but the highest elevations. Fire Weather Watches remain in place for all fire weather zones in western Colorado, and all Utah fire weather zones excepting Zone 485. Once the trough moves overhead, humidity values tick upward just a bit, mainly north of I-70, with minimum humidity values in the 15-20% range. Winds also weaken appreciably, with localized pockets of 20-30 mph gusts confined to areas along the Divide. As a result, only localized critical fire weather conditions are anticipated. This trend of localized critical fire weather conditions continues into early next week, as the building ridge keeps winds on the lighter side, but also keeps things hot and dry.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1120 PM MDT Thu Jun 18 2026

Few to scattered mid-level and cirrus clouds will blanket much of the region throughout the next 24 hours, but VFR conditions continue. Winds will be weaker Friday, but most, if not all terminals should expect 18-22 kt gusts in the afternoon.

FIRE WEATHER

Issued at 934 PM MDT Thu Jun 18 2026

High pressure will slowly erode over the next day or so as a shortwave disturbance crosses the Great Basin. Critical fire weather conditions will remain localized under lighter winds and hot, dry conditions this afternoon. Non zero chances for terrain based, mostly dry thunderstorms emerge this afternoon as well, elevating the chances for new fire starts. This chance increases Saturday afternoon, given the more dynamic environment that develops under the shortwave. Fire Weather Watches remain in effect for nearly all for eastern Utah and western Colorado on Saturday.

Critical fire weather conditions become more localized by Sunday. The threat for additional shower/thunderstorm development continues into Sunday as well. High pressure returns next week with triple digit temperatures likely to return to our low desert valleys. With low relative humidities expected, this will likely include critical fire weather conditions continuing as well.

GJT WATCHES/WARNINGS/ADVISORIES

CO...Fire Weather Watch from Saturday afternoon through Saturday evening for COZ200>203-205-207-290>295. UT...Fire Weather Watch from Saturday afternoon through Saturday evening for UTZ486-487-490-491.