Arctic air surging south could glaze Colorado roads with ice in time for the evening commute Friday as Denver braces for a weekend of bitter, sub-zero cold. National Weather Service meteorologist David Barjenbruch said temperatures are expected to plunge twice Friday — first in the late morning and again in the late afternoon, when snow falling on warm roads has the potential to melt and then harden into an icy crust. RELATED: Everything you need to know about the polar vortex bringing extreme cold to Colorado “We’re used to driving on snow here in Colorado, but ice is a whole other thing,” he said.