Rounds of showers and thunderstorms will bring the threat of flash flooding and travel disruptions from the Ohio and Tennessee valleys to the mid-Atlantic and New England through Friday.
The risk area covers a heavily populated and heavily traveled region of the country, home to tens of millions of people and daily commuters.
A surge in humidity, combined with a very slow-moving front and a series of disturbances moving along it, will favor episodes of downpours, thunder and lightning.
While most of the region will just experience a few doses of heavy rain and thunder, some locations can be hit much harder on one or more occasions through the end of the week.
Cities that could be directly impacted by flash flooding Friday into Friday night include Charleston, W.Va., Washington, Baltimore, Philadelphia, New York City, Boston, Hartford, Conn., and Portland, Maine.
The pattern is part of the same setup that will continue to clobber the central Plains this week.
It has the potential to bring a couple of inches of rain in as many hours to a few communities in the Ohio Valley, mid-Atlantic and New England as well. Some unlucky locations could be hit with 6 inches of rain into the end of the week.
Similar to what occurred in June and July in the Northeast, some streets and highways could be flooded.
The activity will not be limited to the afternoon and evening hours, which is typically the case this time of the year.
Motorists and airline interests should be prepared for delays.
Over the weekend, the corridor of repeating downpours will shrink southward, so that much of New England, the northern mid-Atlantic and part of the Ohio Valley will dry out.
However, that southward shift will grind to a halt.
Flooding problems are possible in Tennessee and North Carolina to parts of Kentucky, Virginia and West Virginia Saturday and Sunday. There is a chance the activity continues on to part of the Virginia Tidewater as well.
An unusually strong push of cool air for early September will move southward along the Atlantic Seaboard into the Labor Day weekend, before July-like heat returns by next week.
While lulls in tropical activity in the Atlantic will continue, a rapid end to the hurricane season in September does not always occur during an El Nino.
After heat has dominated headlines this summer, cool air has finally taken control of the northern half of Europe with no signs of departing anytime soon.
While Tropical Storm Kevin will stay well away from Mexico, its moisture will still lead to an increase in showers and thunderstorms from Baja California to the Four Corners region of the United States.
A stormy weather pattern will prevail through September across much of southern South America.
Steering winds could take Ignacio, as a remnant storm, into the southeastern arm of Alaska or British Columbia during the middle days of next week.
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