For the latest thinking on the tornado and severe weather situation in the East, consult "Tornado Risk DC, Lancaster, Raleigh, Roanoke."
There is the potential for violent thunderstorms, including a few tornadoes, later today from portions of Pennsylvania and New Jersey to northern Georgia and South Carolina. The storms could impact tens of millions of people in the I-81 and I-95 corridors.
Cities from Pittsburgh, Philadelphia and Trenton southward to Augusta and Columbia will be in the zone of potentially damaging and dangerous storms this afternoon and evening. Downpours and locally gusty winds will even reach into Buffalo, the New York City area and part of southern New England and upstate New York.
The greatest threats from the thunderstorms will be wind gusts to 60 mph, golf ball-sized hail, flash flooding and frequent lightning strikes.
There is also the potential for a few tornadoes being produced by the strongest storms this afternoon into the early evening. The area at highest risk for a tornado extends from southern Pennsylvania south through the D.C. area and into southern Maryland, much of Virginia and into central North Carolina.
According to Severe Weather Expert Henry Margusity, "The storm system will change its orientation so that violent thunderstorms, including tornadoes, will be possible in areas that tend to see much less severe weather, when compared to the Plains and Midwest."
Margusity feels that the storm system will have some extra time to pull humid (high dew point) air northward along the coastal Plain of the Southeast and mid-Atlantic.
The rapid inflow of moisture is a component for the most violent storms, including tornadoes.
"The system with its strong wind shear and cold air aloft is hitting the East during its prime season for severe weather," Margusity added.
The problems may extend well beyond highway and airport travel delays and foiled evening outdoor graduation plans. Some communities could be in the dark for hours in the wake of the storms and a small number of trees could be downed, which could block streets or crash into homes.
Large hail could bring damaged vehicles and broken windows.
This story was originally published at 10:00 a.m. EDT, Thursday, May 31, 2012 and has been updated.
A fast-moving snowstorm will sweep through the Plains and Midwest through the middle of the week, but its impacts come during the busiest travel time of the year.
A storm with rain and heavy snow will cause major disruptions and delays for Thanksgiving travel on the East Coast and in the Appalachians.
New York Gov. Andrew Cuomo apologized Monday for his harsh criticism of the National Weather Service's lake-effect snow forecasts.
Areas of snow and ice will create slippery travel for some northern states on Black Friday, while the weather will cooperate for shoppers over most of nation.
Temperatures will plummet across the Minneapolis area following Thanksgiving Day as frigid air holds through the weekend.
Rounds of tropical downpours threaten to cause flooding across the Philippines this week with the danger also spreading to Vietnam.
North Dakota (1896)
Thanksgiving Day Blizzard. "Wind Velocity and snowfall never equalled before."
Destructive windstorm in the Northwest; winds gusting to 105 mph in Cut Bank, MT; 96 mph in Sheridan, WY. Spokane, WA, radio tower downed. Coleville, WA, lumber shed demolished.
Barst, Guadeloupe (1970)
1.50 inches of rain in 1 minute -- world record.