Nearly half of all Americans affected by massive winter storm

Nearly half of all Americans are in the path of a massive catastrophic winter storm as it roars across the country. Governors in 16 states have declared States of Emergency.

Forecasters expect the storm to cripple major cities possibly knocking out power for days.

This as supermarkets have empty shelves as worried residents stock up and long lines are seen outside many stores.

And nearly 5,200 flights have been cadence for the weekend.

NBC NEWS has more.