The National Weather Service office in Grand Junction, Colorado, expected 2 to 4 inches or more of total precipitation across the San Juan Mountains in southwestern Colorado during a storm running from Oct. 21 through Oct. 24, 2026, and with snow levels forecast to hover around 12,000 to 13,000 feet, most of it was expected to fall as rain. Rain instead of snow at that scale puts water straight into creeks and rivers rather than banking it in the snowpack. Flooding, not skiing, was the main concern.
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The San Juans are steep, high and drained by rivers that run through small towns such as Silverton, Ouray and Telluride, so heavy rain can reach homes and roads quickly. Narrow valleys leave little room for water to spread, and mountain highways follow the same drainages that flood. When a storm arrives with warm air, the usual cushion of fresh snow is missing, and any earlier snow on the slopes can add meltwater to the rain.
The NWS Grand Junction precipitation forecast
Unofficial Networks reported on Oct. 20 that NWS Grand Junction expected 1 to 3 inches of total precipitation across portions of the southern Colorado mountains, with the San Juans and southern foothills able to see 2 to 4 inches or more. The precipitation was due to fall from Wednesday through Friday, Oct. 21 to 23, with a separate low bringing weekend mountain snow above roughly 10,000 feet.
Snow levels were the deciding factor. The roundup said levels might stay around 12,000 to 13,000 feet for much of the event, and that “high snow levels may keep much of it falling as rain until colder air arrives later in the week.” Silverton Mountain has terrain above 13,000 feet and was described as one of the more promising spots, but rain could fall across much of the mountain, and no reliable summit totals existed. Telluride and Crested Butte were expected to see mostly rain, with accumulating snow mainly on the highest terrain.
Flood risk in southwestern Colorado, from burn scars to runoff
The same article called flooding “the more immediate concern in southwestern Colorado,” saying heavy rain combined with melting snow from earlier storms could create excessive runoff and dangerous conditions on mountain roads and waterways. FOX Weather’s Oct. 21 coverage reinforced that picture, reporting that a flood watch covered parts of southwestern Colorado, southern Utah, western New Mexico and much of Arizona through Thursday, with a renewed flash flood threat across the Four Corners on Oct. 22.
Burn scars add another layer of risk in the region. A separate NWS Grand Junction discussion issued on Oct. 10, for an earlier storm, noted debris-flow risk on burn scars and said smaller drainages, arroyos and slot canyons could rise rapidly, while adding that confidence remained too low at that time for a flood watch. That earlier text covered a different event, but it shows how the office frames the terrain: a thin margin between steady rain and a flash flood.
Where the rain fits into the wider storm
The San Juans sat at the eastern end of a system that had already produced tornado alerts in Arizona and flooding in Utah. AccuWeather placed the highest flash-flood risk in Arizona, Utah, western Colorado and New Mexico, and said the storm would move slowly through the Southwest and Rockies late in the week, bringing more rain and mountain snow as it reached cooler air. A slow-moving storm is more dangerous for flooding because it keeps feeding rain over the same basins.
Weather.com’s Oct. 21 report said parts of the Sierra and Rockies could see the first significant snow of the season, with rain able to change over to snow at higher elevations. For the San Juans, that change was expected to arrive late, which is why the rain total, not the snow total, carried the risk.
Snow did figure in the longer outlook. The Unofficial Networks roundup said a separate low was expected to bring weekend mountain snow above roughly 10,000 feet, and that Interstate 70 resorts in central Colorado, including Breckenridge, Copper Mountain and Arapahoe Basin, could see snow as temperatures fell, though no resort-specific totals were established. For the San Juans, that later cold air was not expected to undo the earlier rain, only to change what fell afterward.
Elsewhere in Colorado, FOX Weather flagged a small Level 3 of 4 flash flood risk near the Ferris Fire burn scar in the southeastern part of the state, where the FOX Forecast Center said 3 to 5 inches of rain was possible. That area is separate from the San Juans, but it shows that burned ground across the state was part of the forecasters’ concern, not only the mountains of the southwest.
The figures are forecast ranges issued on and before Oct. 21, so actual rainfall could land above or below them. Anyone traveling mountain roads in the region should rely on local road reports and weather service warnings, since flood alerts for a given creek can be issued within minutes.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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