A bitterly cold arctic air mass will push into Colorado Wednesday, with rapidly falling temperatures behind the front expected to arrive during the later afternoon or shortly after sundown in the Denver Metro area. Northeast winds of 20-30mph may accompany the front, with higher gusts possible. Overnight lows Wednesday night fall well below zero, with lows of -10 to -15 Denver, -13 to -18 Castle Rock, and to -20 Fort Morgan possible by daybreak. High temperatures struggle to climb above zero areas north of the Palmer Divide on Thursday. Some moderation in temperatures on Friday with highs in the teens and 20s but still well below freezing. Breezy winds as well on Thursday result in dangerously low wind chills of -30 to even -50 eastern plains, with a wind chill watch posted for Wednesday evening through Friday morning for all of eastern Colorado, from the CO/NM border to the CO/WY border as well as the KS border to the east. Bitterly cold again Thursday night with temperatures falling well below the zero mark.