The major winter storm crossing the nation is causing dramatic declines in temperatures across the central US as arctic air pushes south and east.Some highlights:Casper, Wyoming(Mountain time)In less than 18 hours, from 7:40 a.m. Wednesday to 1:35 a.m. Thursday, the temperature dropped 70 degrees.LIVE NEWS: Winter storm and severe cold sweeps across the USDenver(Mountain time)Dropped 65 degrees in 16 hours.The largest plunge came when temperatures dropped 47 degrees in just two hours Wednesday from 46 degrees at 3:58 p.m. to minus 1 degree at 5:58 p.m.Read moreIn pictures: Winter storm impacts the USAmarillo, Texas(Central time)Dropped 42 degrees in six hours.Wichita, Kansas(Central time)Dropped 36 degrees in nine hours."