Storms to raise localized flood threat across northeastern US, Atlantic Canada

By Alex Sosnowski, AccuWeather.com Senior Meteorologist

October 21,2016; 9:05PM,EDT

 

Rain and thunderstorms will continue to cause travel delays and raise the risk of isolated flooding in parts of the northeastern United States and Atlantic Canada into the weekend.
Rainfall will largely be triggered by a non-tropical storm system tapping into warm, humid air ahead of the arrival of much colder air.

The greatest amount of rain will occur where thunderstorms form and linger for a few hours or more, likely from western and northern Pennsylvania to western, central and northern New York state to northern Vermont and southern Quebec into Saturday.
During Thursday night, 6-9 inches of rain fell in several hours over parts of western and central Pennsylvania and resulted in a highly-localized disaster.
This image was taken several hours after the worst of the flooding near Milesburg, Pennsylvania, on Friday, Oct. 21, 2016. (Photo by Adam Douty/AccuWeather Meteorologist).
Flash, urban and small stream flooding in some communities closed roads and prompted water rescues.
Although rainfall of this nature will continue to be highly localized, it could result in a similar situation for some communities farther to the north and east.
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Even where several inches of rainfall does not occur, sudden downpours can cause brief travel disruptions around major cities from Washington, D.C., to Philadelphia, New York City and Boston into Saturday AccuWeather Chief Meteorologist Elliot Abrams said.
A few thunderstorms can also bring wind gusts strong enough to knock down tree limbs and send loose items flying.
Farther east from Massachusetts, Rhode Island, New Hampshire and Maine to Nova Scotia, New Brunswick, Newfoundland and eastern Quebec, the rainfall will be the result of both tropical and non-tropical moisture and will occur mainly during Saturday.

"There is still a chance the tropical system west of Bermuda develops into a depression or Otto prior to moving northward into Atlantic Canada on Saturday," AccuWeather Meteorologist Steve Travis said.
Even in the absence of full development of this system, there will be strong winds in some coastal areas and heavy rainfall.
Heavy rainfall will be more widespread in this swath and may result in more general problems due to flash and urban flooding, despite prior drought conditions.

Throughout the northeastern U.S. and Atlantic Canada, where leaves have fallen or are being knocked down by rain and wind, roads can be extra slick. Some storm drains may become blocked due to the fallen leaves, which can add to street flooding. Motorists are urged to drive with caution and never attempt to travel through flooded areas.
In absence of the flooding, the rain will help ease long-term dry conditions from New York state to New England.