Snow ploughs in Philadelphia after 2010 'Snowpocalypse'
© AP
Snow ploughs in Philadelphia after 'Snowpocalypse' storm hit US in 2010
National Weather Service warns of "life-threatenting conditions" and "impossible" travel in Washington, with snow also expected in Baltimore, Philadelphia and New York

A blizzard of historic proportions is expected to hit Washington, Baltimore and other East Coast cities beginning on Friday, with snowfalls of more than two feet predicted in some areas.

The National Weather Service has issued a blizzard watch for the Washington area, warning that "potential life-threatening conditions are expected Friday night into Saturday night."

"Travel is expected to be severely limited if not impossible during the height of the storm," the warning reads.

Coupled with the snow - which meteorologists say could be as much as 30 inches deep in Washington - will be high winds that may reach more than 50 miles per hour.

Although current weather models place Washington in the eye of the storm, cities across the Northeast are bracing for the blizzard as well.

New York, Philadelphia and Boston are all expected to see snowfall, though it is unclear how heavy it will be.

NOAA weather map
© APThis image provided by National Oceanic and Atmospheric Administration's (NOAA) National Weather Service Weather Prediction Centre shows an early computer model forecasting the chances of a windy, strong sleet-snow storm hitting the East Coast this weekend. Meteorologists say tens of millions of Americans from Washington to Boston and the Ohio Valley could be walloped by an end-of-the-week snowstorm
Residents of Washington were stocking up on supplies on Wednesday, with shelves at some grocery stores already empty.

Because the intense snowfall is expected to begin on Friday evening and not abate until late on Saturday night, officials have warned that residents of the cities may not be able to leave their homes until Sunday, or even Monday.

The snowfall will not only be long-lasting, but heavy. It could exceed two inches of accumulation-per-hour at times.

If the forecasts come to fruition the storm - nicknamed "Jonas" - could be the biggest in Washington's history. The highest accumulations to date came in 1922, when 28 inches of snow blanketed the city.

After 18 inches of snow hit Washington in 2010, in the third-largest snowstorm in the city's history, the US capital ground to a halt, and took days to get out from under the storm.

This storm could prove even more intense.

While other parts of the US have faced snow and extreme cold this year, the north-east has so far been largely spared.

That is expected to change this weekend.