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Flooding Risk Raised for Midwest, Northeast, Neighboring Canada

February 25, 2011

Concerns for flooding continue through next week as two storms roll through the Midwest and the Northeast and adjoining areas of southern Canada.

First Storm

The storm coming today into Friday traveling from the Midwest to the Northeast U.S. will be the colder of the two storms.

What this means is that snow or a wintry mix will fall from around the central and lower Great Lakes through the northern mid-Atlantic and into New England. Rain will fall over the Ohio Valley through most of the balance of the mid-Atlantic and into southeastern New England and Nova Scotia.

Up north and well inland of the coast the snow and wintry mix will add to the water equivalent of the existing snowpack or will reduce that snowpack by very little.

According to Chief Meteorologist Elliot Abrams, “Farther south and along the coast, heavy rain or the combination of rain and melting snow and ice will lead to urban flooding problems and perhaps some rises on streams and rivers.”

With the ground still frozen in some areas, the water will run off crossing roads, collect in fields, backyards and city streets.

According to Senior Meteorologist and Indiana native Jim Andrews, “In the Ohio and Tennessee valleys into Friday, enough rain can fall without the aid of melting snow to lead to rises on rivers and small stream flooding.”

The Second Storm

A storm is forecast to roll out of the West and cut well up into the Great Lakes region and the St. Lawrence Valley during the first part of next week.

It is this storm that has AccuWeather.com meteorologists, including Elliot Abrams, quite concerned about flooding over the Upper Midwest, the northern mid-Atlantic, much of New England, southern Quebec and Ontario and much of New Brunswick.

Over much of this area, there is substantial snowcover on the ground that will likely survive or will be built up by the storm today into Friday. Of that snowcover, several inches or more of water is locked up, waiting to be released.

This map provided by the National Weather Service shows the amount of water locked up in the snowcover. The pink areas indicate where 6 inches (150 mm) or more of water is locked in the snow. Even in areas with blue shading, or up to a couple of inches (50 mm) of water, there can be urban flooding issues and quick rises on small streams.

The worst case scenario would be a repeat of what happened in parts of the Northeast during January 1996. A surge of warm, humid air, accompanied by significant winds and heavy rain, led to a rapid meltdown of feet of snow and unleashed over 5 inches (130 mm) of water in a matter of hours.

Even if the components early next week are half as critical as that of January 1996, serious stream and river flooding could still occur.

“Generally where there is still significant old snow on the ground, chances are most streams and rivers in that area are also frozen over or clogged with chunks of ice,” Andrews stated.

Andrews added, “The risk of ice jam flooding remains high as a result of these two storms within the next week and beyond.”

Fortunately, this storm and one that follows early next week with their snow and rain will tend to avoid much of the northern Plains. However, flooding concerns go well beyond the next two storms for this area.

What Can You Do?

At this point, there is not a whole lot you can do. Buying flooding insurance for these two events in particular will not work as there is a 30-day waiting period until the policy is in effect in most cases, once the paper is signed. However, it could safeguard you for future threats.

You can make sure there are no big piles of snow around your home that will channel water into your basement. Make sure downspouts are attached and thawed, allowing water to drain away from your home, instead of along your foundation.

Check to see that storm drains in your neighborhood are free of piles of snow or at least so that water has a route to the drains. If this task is too strenuous for you, contact your local highway department.

Have a plan of action in place in case a stream rises suddenly at your location.

Keep up with flood watches and warnings by following your local weather at AccuWeather.com in addition to monitoring local radio and TV forecasts. AccuWeather has a vast network of radio and TV stations it serves throughout the U.S.

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