More than 50 million people across more than a dozen states have been warned to stay at home as it moves north.
The nation's capital, Washington, could lie under a record 30in (76cm) of snow by the time the storm passes on Sunday.
Eight people have been killed, six states have declared states of emergency and thousands of flights have been cancelled.
The weather system affects a huge swathe of the country, from Arkansas in the south to Massachusetts in the north-east.
Supermarkets ran out of food amid a rush for supplies before the first snowflakes fell on Friday.
In summary:
- More than 6,000 flights have been cancelled for Friday and Saturday
- The US federal government closed down at noon on Friday
- President Barack Obama is remain at the White House, officials said
- States of emergency declared in Tennessee, North Carolina, Virginia, Maryland, Pennsylvania, the District of Columbia and parts of other states
- Eight people have been killed in car crashes in Tennessee, North Carolina, Kentucky and elsewhere
- Washington's transport system - the second busiest in the US - will close all weekend
- Many events, including two sold-out concerts by singer Garth Brooks in Baltimore, have been postponed
Comment: 'Sneaker wave'?
This most certainly is not something that "occurs relatively frequently". The tsunami was perhaps caused by offshore seismic activity like subduction on the sea-floor.