With two weeks still left in autumn, a massive winter storm this weekend could impact more than 50 million Americans. Heavy snow, sleet and rain are possible along a 2,000-mile stretch from Arizona to Virginia. States of emergency have been declared in Oklahoma and North Carolina, where roads are being treated and store shelves are empty. The National Weather Service issued a winter storm watch for southwestern Oklahoma, including Oklahoma City, through Saturday night. The weather service expects up to four inches of snow, in addition to a thin layer of ice in some areas. In Houston, authorities activated their emergency operations center. The National Weather Service issued a flash flood watch, since a storm system could bring up to 10 inches of rain in some areas. The flooding could impact a broad region extending down to the Gulf Coast, with the heaviest rainfall hitting Friday night into early Saturday. The coastal region could even see damaging winds and isolated tornadoes. To the north, snow and freezing rain is forecast for eastern New Mexico and the Oklahoma-Texas panhandles. After hitting Texas, the storm is forecast to move across the Southeast. The Mississippi Emergency Management Agency is telling people to prepare for up to three inches of rain. In Louisiana, the rain could prompt flash flooding.