Arctic storm continues frigid march eastward

A jogger steps carefully across snow-covered street Wednesday in Denver.   (David Zalubowski / Associated Press)

A pedestrian walks along Center Street as snow falls Monday in downtown Casper, Wyo. Temperatures in Casper are expected to dip below zero Tuesday and Wednesday.   (Alan Rogers / Associated Press)

The snow-covered Bridger Mountains are shrouded with clouds on a sub-freezing afternoon in Bozeman, Mont.  (Adrian Sanchez-Gonzalez / Associated Press)

A bicyclist guides his ride through the snow Wednesday in Denver.  (David Zalubowski / Associated Press)

A couple, braving the cold temperatures walk their dogs on a snow-covered path in Bozeman, Mont.  (Adrian Sanchez-Gonzalez / Associated Press)

A Marquette Department of Public Works snow-plow truck gets a tow from a front-end loader while snow falls in Marquette, Mich.  (Ryan Jarvi / Associated Press)

Alan Messner shovels the sidewalk in front of Surplus Outlet in downtown Houghton, Mich., after an early season storm.  (Dan Roblee / Associated Press)

Snow falls in downtown Marquette, Mich.  (Elizabeth Bailey / Associated Press)