A storm moistening as it crosses the central Rockies will tap enough cold air to drop heavy snow over a part of Colorado and Wyoming beginning late Tuesday.

As the instigating storm tracks eastward over the Intermountain West, rain will break out in earnest over Wyoming Tuesday. At first, snow will keep to the mountains, but the snow level will lower to the open plains and valley floors Tuesday night.

Rain and snow will also crank up southward over the northern half of Colorado.

The threat of heavy snow will last well into Wednesday between east-central Wyoming and the eastern slopes of northern and central Colorado.

Higher-end snowfall above 7,000 feet will reach 1 to 2 feet in areas crossed by highways I-70 over the Colorado Divide, and I-80 through central and eastern Wyoming. Substantial snow will also cover stretches of I-25 from Cheyenne to Casper.

Needless to say, this storm will bring full-on winter driving conditions to parts of both states.

The weather will improve markedly on Thursday.

Story by AccuWeather.com Senior Meteorologist Jim Andrews.