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.
Tropical Rainstorm Matmo will bring heavy rain to Korea and Japan this weekend.
Strong and severe thunderstorms from Canada and the northern Plains Thursday will shift into the Midwest and Ohio Valley in time for the weekend.
Former Typhoon Matmo continues to wreak havoc across portions of China.
A tornado touched down and wreaked havoc at Cherrystone Campground in Virginia on Thursday morning, causing two fatalities and nearly two dozen injuries.
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An Air Algerie flight carrying 116 people disappeared from radar as it traveled from Burkina Faso to the Algerian capital, the Associated Press reported, as storms pushed south of the area of lost contact.
Tucson, AZ (1952)
60-mph winds ripped roofs off an apartment complex and an airplane hangar, sweeping dust and sand through the city and leaving 200 persons homeless.
North Carolina (1975)
Lightning killed 13 cows during a thunderstorm at Kenansville. Heavy rains elsewhere in the state forced the Tar River out of its banks at Greenville, causing 14 families to evacuate their homes.
New York (1975)
Severe thunderstorms in western and central NY: lightning struck a city park in Rochester injuring 12 children, all were playing on a metal jungle gym. One patrolman described the scene as if "someone threw a stick of dynamite in the middle of the crowd and it blew."