Accompanying the risk of thunderstorms with strong winds and large hail into Friday evening is the potential for tornadoes.
The prime threat area for tornadoes with this event will be bounded by the Pennsylvania Turnpike to the north, I-81 to the west, I-95 to the east and I-40 to the south.
According to Severe Weather Expert Henry Margusity, "The tornado-producing, isolated storms are likely to form out in front of a squall line forming up over the Appalachians this afternoon."
This puts some major population centers in the risk area and includes Lancaster, Gettysburg and York in Pennsylvania; Baltimore, Frederick and Hagerstown in Maryland; Washington, D.C.; Charlottesville, Richmond and Roanoke in Virginia and Greensboro, Raleigh and Winston-Salem in North Carolina.
"We could also see a couple of tornado-producing storms in western Pennsylvania, in the Johnstown area," Margusity said.
AccuWeather.com meteorologists are not expecting a large number of tornadoes, but are concerned that the tornado risk is setting up in a heavily populated area. Because of this there is substantial risk to lives and property into Friday evening.
Even areas outside of this zone are at risk for damaging thunderstorms and the potential for a tornado reaching across southern Pennsylvania to southern New Jersey, southward to northern and eastern Georgia into South Carolina.
Powerful storms can also reach across the Delmarva Peninsula Friday evening.
A line of thunderstorms with heavy rain and gusty winds is expected to also poke northward into western New York state and the Niagara region. Winds during and immediately behind the front associated with the storm can make for rough waters on lakes Erie and Ontario.
The remnants of the severe weather in the form of heavy rain, thunder, lightning and gusty winds will then swing across coastal New Jersey, the New York City metro area, eastern upstate New York and into New England overnight and into Saturday morning.
The strongest storms will prowl the mid-Atlantic and southeastern United States between 2:00 p.m. and 9:00 p.m. EDT.
People are urged to keep an eye out for rapidly changing weather conditions and heed warnings as they are issued. Seek shelter indoors, away from windows and canopies of trees as the storms approach.
The storm system has had a history of downing a substantial number of trees on its tour of the South Central states. A number of these included trees on vehicles and into homes.
Some locations will be hit by more than one storm or downpour.
According to meteorologist Bill Deger, "there is also the potential for flash and urban flooding with the setup, as the ground is rather wet from recent rain events."
In the wake of the storms, much cooler and less humid air will press to the Atlantic coast this weekend.
This story was originally published at 8:00 a.m. EDT Friday, June 1, 2012.
As millions prepare to take part in Memorial Day weekend events, showers, storms and a potential tropical system could threaten outdoor activities and travel plans during the extended weekend.
A developing tropical system northeast of the Bahamas will approach the southeastern coast of the United States with downpours, building surf and an increasing breeze during Memorial Day weekend.
Severe weather, including the risk of tornadoes and flash flooding, will continue into Memorial Day weekend.
Rainy weather will help to lessen the severity of the drought around Colombia and Venezuela in the coming months while drier-than-normal conditions make matters worse for the drought in Chile and northeastern Brazil.
This weekend will be the biggest racing weekend of the year with three major races drawing in millions of viewers from around the globe.
Jefferson, UT (1992)
Hail accumulated to a depth of 1 inch.
San Antonio, TX (1992)
29.28" of rain since January 1 -- already more than the annual average of 29.13."
Kansas City, MD (1995)
11.07" of rain so far in May - wettest May on record.( 12.75" total for month)