By Alex Sosnowski, AccuWeather senior meteorologist
July 5,2017, 3:03:29PM,EDT
As cooler air begins to advance from Canada, rounds of drenching rain and severe thunderstorms will sweep through the northeastern United States to end the week.People heading out through Friday night may want to take an umbrella and a pair of waterproof shoes as tropical moisture will spill northeastward ahead of the cool push into Friday.
From Thursday to Friday morning, a zone of heavy rain will precede the risk of severe weather in part of the region.
The heaviest rain will extend from the Ohio Valley to part of the central and southern Appalachians to the mid-Atlantic coast on Thursday and Thursday night.
The rain can come down fast enough to slow travel on the highways and create a low cloud ceiling and low visibility at airports from Nashville, Tennessee, and Cincinnati to Pittsburgh, Philadelphia and Washington, D.C., to perhaps New York City. Minor incidents of flash and urban flooding can occur as well.
However, the rain will also help to boost soil moisture and allow lawns to green up. Part of the region has been experiencing abnormally dry conditions of late, according to the United States Drought Monitor.
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During Thursday night and Friday, the locally heavy rain will affect part of southern New England with the potential for similar impacts as that farther south from Thursday.
"Clouds and rain from Thursday and Thursday night may inhibit the formation of thunderstorms and severe weather in part of the region on Friday," according to AccuWeather Senior Meteorologist Kristina Pydynowski. "However, that may not be the case everywhere."
Areas from portions of southern Illinois and Indiana to northwestern Pennsylvania, western and northern New York face the greatest chance of severe thunderstorms on Friday and Friday night.
"The greatest risks from the strongest thunderstorms will be damaging winds, blinding downpours and isolated flash flooding," Pydynowski said. "There may also be hail, and an isolated tornado cannot be ruled out."
Major cities that could be hit with severe weather on Friday include Indianapolis and Fort Wayne, Indiana; Cincinnati, Cleveland, Dayton and Columbus, Ohio; Detroit; Erie, Pennsylvania; Buffalo and Rochester, New York; and Toronto and London, Ontario.
It is possible some storms survive well into Friday night as they press southeastward into the Appalachians.
During this weekend, cooler and drier air will gradually take control.
Highs ranging from the 80s to middle 90s F with high humidity will be replaced with highs ranging from the lower 70s to the middle 80s with low humidity.
Spotty showers and thunderstorms may still affect the region on Saturday, especially from the Appalachians to the Atlantic coast. The air should be dry enough to prevent shower activity west of the Appalachians.
By Sunday, most of the region can expect some sunshine with low humidity for early July. Some showers and thunderstorms may sneak into part of the central and northern Great Lakes region later in the day.