A zone of thundery rain with the risk of flooding and travel delays will occur into the weekend from the northern Plains to the central Appalachians and part of the mid-Atlantic.
The weather will go well beyond making cloudy skies and gloomy conditions during the daytime for the third month of summer.
In this pattern, an individual downpour can be enough to cause isolated urban flooding and commuter chaos.
As the downpours repeat in the coming days, the risk of flash flooding may expand to a more regional basis and the potential for flooding along streams will increase.
According to AccuWeather Senior Meteorologist John Gresiak, "Some locations can be hit with 6 inches of rain during the next several days."
Low-lying areas over the countryside, poor drainage areas in towns and cities can quickly be inundated as downpours increase in intensity and number during the afternoon and evening hours each day. However, the pattern also favors downpours that can occur around the clock.
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Blinding, torrential downpours and isolated severe thunderstorms can disrupt ground and airline travel at times from Minnesota and Wisconsin to Virginia and North Carolina.
Major cities that are likely to have multiple disruptions and the greatest risk of flooding incidents include Minneapolis, Chicago, Indianapolis, Cincinnati, Pittsburgh, Washington, D.C., and Charleston, West Virginia.
Some downpours will occur farther north and east, but that rain will be less frequent and the flooding risk will end before the weekend.
Motorists are urged never to drive through flooded roadways as water levels may quickly rise and the pavement beneath may have been washed out. Only a couple of feet of moving water can sweep a vehicle away.
Home and business owners may want to make sure their sump pump is in working order as the pattern can cause basements to flood.
A series of disturbances will roll southeastward along a boundary separating cool air and low humidity lingering to the north and east from a mass of building hot and humid air to the south and west.
Nearest the rim of hot and humid air, thunderstorms will be the most intense and can bring isolated incidents of damaging wind gusts, frequent lightning strikes and hail.