Powerful storm hammers eastern United States with powerful winds, kills 21
Residents survey damage after a tornado struck a residential area on Sunday in Albany, Georgia. REUTERS/Tami Chappell

A powerful storm system that killed at least 21 people in the southern United States over the weekend was expected on Tuesday to bring heavy snow and wind gusts to the East Coast, making morning driving conditions hazardous.

Northern Pennsylvania, central New York and Maine were expected to sees snowfalls of up to 9 inches (23 cm) with wind gusts of 25 mph (40 kph), the National Weather Service said.

"Only travel in an emergency," it said in an advisory.

Flood advisories and watches were in effect for coastal areas throughout New England until midday.

The storm unleashed deadly twisters in Mississippi and Georgia over the weekend before turning cooler as it advanced on the Northeast on Monday and into Tuesday. It was expected to head into Canada by Wednesday, the service said.

The weather system killed 16 people on Sunday in Georgia, according to a tally by the Storm Prediction Center in Oklahoma.

Georgia Governor Nathan Deal extended a state emergency declaration to 16 counties and said President Donald Trump had called him on Sunday and promised he would be "ready and willing to respond" to an expected request for federal disaster relief.

(Reporting by Brendan O'Brien in Milwaukee; editing by John Stonestreet)