textproduct: Grand Junction

KEY MESSAGES

- Storms are expected to be more isolated Friday. A few strong thunderstorms capable of localized heavy rainfall and small hail are still possible though, primarily over Colorado's high terrain.

- Terrain-driven showers and thunderstorms remain possible through next week.

- Temperatures begin to increase again through the weekend and next week.

DISCUSSION

Issued at 1029 PM MDT Thu Aug 13 2026

ISOLATED FLASH FLOOD AND HAIL CONCERNS FRIDAY:

Southwesterly flow around the western edge of a broad high pressure system continues Friday and through the weekend. Though Thursday marked the expected peak in moisture, this slowly- changing pattern will maintain daily chances of precipitation for the foreseeable future, though storm impacts are anticipated to diminish.

Though the last two days saw appreciable midday instability for this region of the country, storms have often been unable to maintain strength for long durations due to lacking shear and dense clouds quickly filling in during afternoons. The story could be similar Friday. At this moment, models are consistent with each other in lesser cloud cover existing Friday morning over the high terrain near the Divide, with denser cloud cover residing in eastern Utah. This should leave the door open for another day of increasing CAPE through the late morning over much of western Colorado. Also working in the storms' favor is the potential for marginally increased shear as a mild jet streak works its way through the southwesterly flow. On the other hand, moisture is on the decline, as mentioned before, with PWAT's falling below 150% of normal for much of the region. All things considered, most stronger storms capable of small hail and localized heavy rainfall (or the flash flooding concerns that come with it) are expected to stay confined to Colorado's high terrain. Unless areas near or west of the CO-UT border see mostly sunny morning skies Friday, the likely storm mode for these regions will be stratiform rain showers. These storms would still be capable of producing wetting rains while minimizing hydrologic concerns, but a stray stronger storm or two should not be ruled out just yet. All vulnerable areas (especially including burn scars) across the entire CWA will still be at risk of flash flooding or debris flows Friday in spite of the more localized nature of storm coverage.

WET WEATHER PERSISTS:

Even as moisture returns to near-normal through the weekend and early next week, southwesterly flow will support daily chances of precipitation focused around the mountains. Lacking upper- level support through the mid-week will likely mean storm impacts will be on the milder side, but keep up-to-date over the coming days for more details. Model guidance diverges significantly by Wednesday, but there is some potential for an uptick in activity late next week as a shortwave develops over the western CONUS. Without model agreement, uncertainty leaves this potential system as nothing more than an interesting possibility on the horizon, and any speculation on details will have to wait until we see model guidance converge. Otherwise, look for temperatures to begin to rise again with highs expected to return to ~5 degrees above normal by the middle of next week.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1152 PM MDT Thu Aug 13 2026

Isolated showers and thunderstorms are ongoing and will continue overnight. In general, showers will be light and TAF site impacts are unlikely. Isolated to scattered showers and thunderstorms will begin around 18Z and continue through the evening. Primary concerns with this activity are lightning and brief drops to MVFR conditions if stronger showers and storms move over TAF sites. Otherwise, VFR conditions will prevail. Winds will be light and variable overnight, but gusts up to 20 kts are possible at a few sites in the afternoon.

GJT WATCHES/WARNINGS/ADVISORIES

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