textproduct: Grand Junction

KEY MESSAGES

- Warm and windy conditions prevail through Saturday with an increase in afternoon shower and thunderstorm activity Sunday.

- Daytime highs remain 5 to 10 degrees above normal through Sunday before a shift to cooler temperatures next week.

- Cool, wet and unsettled weather is expected through much of next week as moisture continues to feed into the area.

DISCUSSION

Issued at 1038 PM MDT Fri Sep 11 2026

WINDY AND WARM WITH ISOLATED STORMS THIS WEEKEND:

Modest moisture has settled in over the region, promoting sparse, weak showers and thunderstorms over Colorado's west slope. This comes amidst warm zonal upper-level flow set up across the majority of the western CONUS. Decent mixing underneath the strong flow paired with a modest pressure gradient has supported and will continue to support gusty afternoon winds. In addition, with low- levels on the drier side, showers will also contribute to windy conditions should gusty outflow winds develop. Over the next 48 hours as moisture continues to creep upwards, look for storms to increase in coverage, particularly over the high terrain. Impacts should remain relatively isolated Saturday, but we could see storm coverage become more scattered on Sunday as the next strong push of moisture begins to move in.

COOLER AND WETTER PATTERN MONDAY AND BEYOND:

As we begin the work week, a powerful trough will push into the PacNW, pushing flow across the southwestern CONUS to southwesterly. This pulls subtropical moisture further inland towards us. As such, by Monday, look for the strong plume of moisture to be centered over the CWA. PWAT anomalies are anticipated to be near or exceed 200% of normal on Monday, pushing or breaking records for this time of year. The ECMWF Ens is more bullish on the moisture, but even the GFS Ens is indicating PWAT's should be a sure-thing to exceed the 75th percentile. Either way, this pool of moisture surging through the region will be enough to prompt our next round of widespread showers and thunderstorms.

With mid-level moisture already in place and only strengthening over the coming days, cloud cover should generally be ample, including in the morning. This will dampen storm potential, potentially enough to push storm mode more in a stratiform direction. However, dynamic forcing looks to be on the more favorable side with this system, perhaps the most impressive that we've seen in weeks. For one, by Monday we are expected to fall underneath the right entrance region of a powerful jet. In addition to jet placement, overnight Sunday into Monday morning look for cold front pass through. Both factors will go towards supporting discrete storm development. With this, at the very least we should expect to see embedded stronger storms in stratiform rainfall, if not widespread discrete storm development. Wherever discrete storms do develop (whether they be isolated or widespread in nature), localized heavy rainfall will also be likely, especially in areas where the low-level atmosphere is able to significantly moisten up over the weekend. As far as QPF goes, the NBM is heavily favoring southwestern- facing slopes of the San Juans, Grand Mesa, and West Elk Mountains. In these locations, the NBM probability of exceeding a half inch of rain Monday is over 75%, though this could be an overestimate if rain stratiforms out. Northeastern-facing slopes are expected to see lower rain totals, though with a quarter inch of precipitation still likely according to the NBM (>50% chance), hydrologic concerns would still be on the table. That being said, with a few days left to go until the event, it is key to understand that there are too many uncertain factors left to be figured out before we can speculate on the likeliest scenario. Stay tuned for future updates, especially once we receive hi-res model guidance.

Though the combination of highly anomalous moisture and reasonably strong forcing is most potent on Monday, active weather looks to stay relatively strong throughout the work week. The pool of moisture looks to lock in over the West Slope, and the jet continues to stretch across the Intermountain West. Without a clear frontal boundary or shortwave accompanying the mid-to-late week pattern, impacts could become even more conditional on morning cloud cover, but that is a problem that we cannot resolve at this point in time. Ensembles are in step with each other that moisture dissipates on Friday, but even then there is no indication that we will see PWAT's fall below normal, so look for a weakening in storms, but not a complete dissipation.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 1151 PM MDT Fri Sep 11 2026

Overnight winds will generally be light and terrain driven with isolated showers and storms moving through the region from west to east. Precipitation chances will continue through the TAF period, most notably at the mountain terminals Saturday afternoon. Gusty winds up to 25-30 knots are also possible Saturday afternoon.

GJT WATCHES/WARNINGS/ADVISORIES

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