Here's what we know about the winter storm hitting the eastern United States:
— What is it? Possibly one of history's 10 worst winter storms to hit the East Coast. Heavy snow and high winds are moving across the northern mid-Atlantic region. Washington, Baltimore and New York have been toppled with more than two feet of snow and it's still falling.
— Why now? All the ingredients have come together to create a blizzard with brutally high winds, dangerous inland flooding, white-out conditions and even the possibility of thunder snow, with Washington at the epicenter, forecasters said. The storm initially picked up warm water from the Gulf of Mexico, then gained much more moisture from the warmer-than-usual Gulf Stream off the East Coast.
— How long? The snow arrived Friday afternoon in Washington, and it's expected to continue into Sunday as the slow-moving storm moves up the coast.
— How bad? Life-threatening conditions are possible as the storm moves from Kentucky and Tennessee through the Virginias and up the East Coast. At least 18 deaths were blamed on the weather, resulting from car crashes, shoveling snow and hypothermia. Extremely heavy snow and high wind gusts could reduce visibility to zero, toppling trees and causing power outages. Forecasters expect flooding, though not as bad as Superstorm Sandy's. Travel bans for nonemergency vehicles are in effect until Sunday morning in New York City and Baltimore.
— Is snow the only worry? Snow is only a small part of this blizzard. It is a blizzard because of high sustained winds. Those winds reached near hurricane levels with 70 mph in Wallops Island, Virginia, said forecaster Patrick Burke at the National Weather Service's Weather Prediction Center in College Park, Maryland. From Virginia to New York sustained winds topped 30 mph and gusted around 50 mph, he said.
On the Eastern Shore, Dewey Beach, Delaware, and Langley Air Force Base, Virginia, recorded hurricane-force 75 mph winds, the weather service's storm tracking page reported.
— How much? Forty inches of snow fell in a rural area of West Virginia, not far from Harper's Ferry, according to unofficial statistics at the National Weather Service.
Glengary, West Virginia, topped the charts for the East Coast blizzard with 40 inches, but 67 locations — mostly in West Virginia, Virginia and Maryland — reported at least two feet of snow. Dulles International Airport outside of Washington was just behind at 30 inches of snow, which puts it third all time for that location.
Snow is expected to keep falling until late Saturday or early Sunday morning. High winds are making it hard to get accurate measurements of snowfall except in official locations, meteorologists said.
— What to do? STAY INSIDE! Authorities pleaded with people to hunker down by 3 p.m. Friday and stay there until the storm is over.