Powerful storm system moves across US

More than seven million Americans are under winter weather alerts and about 300,000 under blizzard warnings Sunday morning amidst a powerful storm system that blanketed parts of the western Plains with snow and unleashed violent tornadoes in Texas.More than seven million Americans are under winter weather alerts and about 300,000 under blizzard warnings Sunday morning amidst a powerful storm system that blanketed parts of the western Plains with snow and unleashed violent tornadoes in Texas.