New York - A deadly winter storm swept the eastern United States on Thursday, spelling drudgery for millions and tragedy for a few, including an expectant mother killed by a snowplough.
US media counted some 16 to 18 people dead as a result of the storm, which dropped a thick blanket of snow over eastern cities overnight and shut down federal government operations in Washington.
One of the casualties was a 36-year-old pregnant woman, struck and killed by a snowplough in a New York parking lot.
Her baby was delivered alive by caesarean section but remains in critical condition.
In Washington, a man from a local psychiatric hospital was found dead in the snow, Mayor Vincent Gray said.
The National Weather Service warned that heavy snow would continue overnight in the northeast, "but will begin to taper off from south to north through the morning hours on Friday".
Thousands of travellers were stranded as major air hubs such as Atlanta and New York, were closed down. Washington's Dulles International reported 35cm of snow.
Some 6 500 flights were cancelled outright, and more than 3 800 delayed.
Nearly 800 000 homes and businesses lost power across 11 states along the eastern seaboard, with 340 000 outages in North and South Carolina, the department of energy said on Thursday afternoon.
In Washington buses were cancelled and city services struggled to keep even major roads open.
Schools were shut and the streets of the capital eerily deserted as federal workers stayed home or worked to scrape snow off sidewalks and driveways.
Even the White House cancelled its daily news briefing, as skiers appeared nearby on the National Mall, the large esplanade at the centre of Washington.
New York, which saw the same abundance of snow on Thursday morning, was under a weather advisory until 06:00 on Friday, with 30cm of snow expected for the city.
Mayor Bill de Blasio warned New Yorkers that public transportation remained the best option for travel and that trash collection had been suspended.
Meanwhile, "thundersleet" a foul mix of lightning storms and mixed precipitation, brewed in Virginia and headed north.
Broadcasters fell over themselves to find superlatives to describe this "Snowmaggedon", dubbed "historic" and "mindboggling".
"This storm is dangerous. Road conditions are treacherous", said governor Pat McCrory of North Carolina, a state where President Barack Obama had declared a federal emergency.
In Connecticut, governor Dannel Malloy declared a state of emergency asking the federal government for help in areas of the state experiencing road-salt shortages.
The storm is only the latest severe weather to hit the eastern United States in what was already the worst winter in 10 years.
But experts predicted it would have little long term economic impact, perhaps knocking only around 0.1% off first quarter GDP growth, according to economic Doug Handler of IHS Global Insight.
Although the storm would mean a short term drop in economic activity, consumers would spend more in heating fuel.