textproduct: Grand Junction

KEY MESSAGES

- Valley rain and mountain snow returns to the forecast this weekend favoring the southern mountains and adjacent foothills.

- Quiet conditions return briefly Sunday afternoon and Monday before another round of precipitation arrives during the middle of next week.

DISCUSSION

Issued at 1149 AM MST Fri Nov 13 2026

MOUNTAIN SNOW AND VALLEY RAIN RETURNS:

Multiple troughs are anticipated to make their way through the Intermountain West over the coming week, bringing snowfall to the mountains and rain showers to valleys. Presently, two troughs are situated to our west, one offshore of the PacNW and one skirting along the southwestern border of the US. The former will carry with it a moderate surge of AR moisture, most of which is expected to get held up on the Sierra Nevada. The latter is delivering its own pool of potent moisture as well. Ensembles are keying in on both sources of moisture transiting the southwestern CONUS and into our CWA, arriving before midnight tonight. As this plume pushes through the warmer valleys, rain showers are expected to develop in the Four Corners region and up towards east-central Utah. By midnight, storms will be climbing into the San Juan mountains where temperatures will be below freezing, hence snow will dominate. Snow levels at the onset of this moisture are hovering around 9000 feet before fropa near sunset drops them another thousand feet and quickly cooling overnight temperatures bring them down to 6000-7000 feet by the end of the event early Sunday morning. The strongest snow rates are expected to hit in the early to middle portion of the event though, likely between 6 AM and noon, and so the bulk of impactful accumulations are likely above 9000 feet. As it stands, above this elevation, accumulations are expected to rest between 4-8 inches in the San Juans (and below 4 inches in the central Colorado mountains and Grand Mesa), though it is worth noting that the NBM 90th percentile is still suggesting that accumulations over a foot in the San Juans at pass level and above are not improbable. Still, given the consistency between forecasts up to this point, we see the likeliest scenario being widespread accumulations under a foot with only localized heavier snowfall exceeding this threshold. Regardless, given the expected snowfall and this possibility of higher accumulations, conditions have warranted a winter weather advisory, which has been issued from midnight tonight through 9 PM Saturday for the southern slopes of the San Juans over 9000 feet. Given the lack of snowfall during overnight periods, it is possible that snow will struggle to stick to roadways, so travel impacts may be somewhat localized throughout the day tomorrow. Regardless, it is imperative to be weather aware and be cautious should you be driving through the mountains tomorrow.

Precipitation lulls beginning Sunday afternoon and through Monday before another wave descends into the western CONUS on Tuesday. Early indications are for similar moisture content to accompany this system, but the overall complexion of the storm is still uncertain. Models are depicting a strong front to accompany the wave, but its passage does not currently align well enough with the heaviest precipitation to support higher snow water ratios. However, given the complex nature of the upper-level pattern at this time, it's uncertain if the timing of the moisture and fropa will hold to this timeline or shift. This would have notable implications on snow accumulations, and so we cannot speculate on that detail either at this time. We are confident that there will be active weather at this time though, so it is safe to plan for potentially impactful precipitation at some point during Tuesday and Wednesday. Furthermore, there is signal of an additional wave moving in quickly behind this one. Additional details on precipitation with that wave will be elaborated on when model guidance becomes clearer.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1030 AM MST Fri Nov 13 2026

High clouds will continue streaming in from the west throughout the day, gradually increasing in coverage through the afternoon. Moisture will increase tonight into Saturday, with light showers possible across all TAF sites. Cigs will begin lowering after ~06Z. In some locations, particularly the mountain terminals, this could lead to cigs below ILS breakpoints. In addition to cigs dropping, visibilities will also be on the decline as precipitation chances increase throughout the area. All that being said, VFR conditions will prevail to begin the TAF period, but beyond 06Z, those conditions could fall to lower flight categories.

GJT WATCHES/WARNINGS/ADVISORIES

CO...Winter Weather Advisory from midnight tonight to 9 PM MST Saturday for COZ019. UT...None.