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    East Flash Flood Risk Redux, NYC, Philly, Baltimore

    September 27, 2011; 2:50 PM ET
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    Street flooding in State College, Pa., Tuesday morning. Photo from AccuWeather.com's Jesse Ferrell. More photo's are posted on his <a href="http://www.facebook.com/media/set/?set=a.264259970274824.73230.227009963999825&type=1"target=blank"">Weather Matrix page</a>.

    The risk of localized flash flooding has re-emerged in the East and includes not only the major cities of New York, Philadelphia, Washington, D.C., Baltimore, but other cities and rural areas.

    As Meteorologist Bill Deger pointed out, the overall pattern will remain wet and unsettled through the week over much of the East. Most of places will simply have showers and an occasional thunderstorm with only minor travel-related problems and foiled outdoor plans.

    However, at the local level, the rain will intensify and cause more serious problems every once in a while.

    Most of the mid-Atlantic states, including areas from Richmond, Va., to Hagerstown, Md., Harrisburg, Williamsport and Scranton, Pa., to Albany, Elmira and Binghamton, N.Y. and Trenton, N.J. will be hit with downpours through Wednesday.

    By Thursday, the bulk of the downpours will again focus over eastern New York state, but will include New York City an more of New Jersey, and will expand eastward into New England and neighboring Quebec, including Hartford, Boston, Burlington, Vt., Portland, Maine, and Montreal.

    Rainfall could exceed an inch in an hour's time, where downpours persist, with or without thunderstorms.

    This graphic supplied by the National Weather Service Flash Flood Guidance reveals that an inch of rain or less per hour is all that is needed to cause flash flooding in areas shaded in red or dark red. Fortunately, areas hit hard by heavy rain Monday evening in Ohio, western Pennsylvania and West Virginia caught a little break from the downpours Tuesday.

    This type of rainfall can quickly run off the saturated ground and into streams in rural areas.

    Much less rainfall can lead to flooding in urban areas, including streets and catch basins.

    Remember, never drive through flooded roadways. Stay away from earthen banks along streams.

    In recently flooded West Pittston, Pa., which lies along the banks of the Susquehanna River, mud-clogged storm drains led to serious street flooding late last week during a downpour.

    The atmospheric setup from last week remains with a storm over the Midwest continuing to funnel in Gulf of Mexico and Atlantic moisture. The sunshine that broke through much of the East this past weekend was, well, just a bonus.

    Disturbances rotating around the big storm in the Midwest will enhance the rainfall at the local level on occasion. If the rain occurs at the wrong place for too long of a period of time, streets can turn to rivers with little notice and small streams can become raging torrents and overflow their banks.

    Localized flooding downpours will also continue to affect part of the South through midweek. In the South from Texas to Florida and the Carolinas, it is the tail end of a front that can lead to not only localized heavy rainfall, but also isolated severe thunderstorms.

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