The forecast calls for 4-8 inches of accumulated snow and 10-15 mph winds. Visibility will be reduced to a half mile, the weather service said, and mountain travel may be hazardous.
The snow level might fall to 10,000 feet, depending on how low temperatures fall.
The weather service on Tuesday warned that the developing storm that could dump moderate to heavy amounts of snow on the San Juan Mountains on Wednesday and Thursday, as showers and thunderstorms hit cold air in the mountains.
In Montezuma County, showers and thunderstorms are expected Wednesday, with a high temperature near 53 degrees and a low of 44. The likelihood of rain decreases on Thursday and Friday, and daytime high temperatures are expected to be in the lower 60s.
The weather service emphasized Tuesday that its forecast remains uncertain because of the warm nature of the storm system. It said its forecast may change as more information becomes available.
