Areas from New England through the Ohio River Valley will be at risk for damaging thunderstorms and flash flooding into Wednesday night.
This is the same storm system that brought thunder, hail and gusty winds to the northern Plains and some of the Midwest on Tuesday.
As a cold front swings through the region on Wednesday, two very different air masses will collide. The drier air arriving from the northern Plains will meet the steamy air hanging on over the eastern third of the nation.
The merge of dry air and very moist air will create favorable conditions for thunderstorms, some of which may be severe.
The main threats with these storms will be torrential downpours, damaging wind gusts in excess of 60 mph and a few incidents of large hail. A couple of the strongest storms can also produce a short-lived tornado.
Affected cities stretch from Cape Girardeau in Missouri, to Cincinnati and Pittsburgh, but also as far north as Syracuse, Albany and Hartford.
Pittsburgh received drenching downpours Wednesday morning, leading to flash flooding in the area. Another round of storms is forecast for the Steel City later Wednesday, which will extend the threat for more flooding.
Wednesday night the storms will continue to drift eastward and may reach New York City, Philadelphia, and Washington, D.C. before weakening.
Another area of the country will experience locally severe storms Wednesday evening. A corridor from eastern Wyoming to northwestern Kansas could be hit with gusty winds and hail.
Later in the week, the front will slowly drift to the east with the threat of torrential downpours near the coast.
This will bring a refreshing end to the oppressive humidity felt across much of the Northeast for the weekend. However, the muggy weather will likely still have a bit of a hold along the Atlantic Coast.
Another visit from the Polar Vortex will deliver unseasonably cool air to the Midwest, preceded by rounds of thunderstorms, including severe weather.
Heat-related dangers will be on the rise over the weekend for much of the Northwest as scorching heat settles in.
As the Northeast continues to clean up from destructive storms early this week, more rounds of severe weather and flash flooding loom for early next week.
Parts of the South will get major relief from heat, humidity and storms next week while other locations will be at greater risk for flash flooding.
Yellowstone National Park's Firehole Lake Drive was closed Thursday, July 10, as portions of the roadway's asphalt melted amid the summer's recent heat wave in the Northwest.
Virginia Beach, VA (1990)
8.9 inches of rain in the Pembroke section of the city resulted in major flooding.
Columbus, OH (1992)
A total of 5.11 inches of rain caused major flooding in the city.
Pinellas Co., FL (1992)
A tornado blew a catamaran into a car, injuring six people.