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    2011 Flooding Risk Elevated for Midwest, New England

    February 19, 2011; 4:55 AM ET
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    Play video AccuWeather.com's Bo Zhang reports on the flooding situation in this video.

    This year, as has been the case in recent years, could bring major flooding to parts of the Upper Midwest and New England.

    Minor flooding is nearly routine in the late winter and spring along streams and rivers. Moisture-laden storms and a thaw of 6 to 12 inches of snow are rather common during the last part of winter into spring.

    However, this year, lingering heavy snow cover and the water locked up in that snow have the clock ticking on the flood potential time bomb.

    The thaw from the week of February 13 through the 18th helped some areas substantially, but not enough in the Upper Midwest, New England and parts of New York state.

    Parts of this region still have 3 inches of water or more locked up in the existing snow and ice cover.

    As additional storms swing through these areas over the next several weeks, additional snow will be deposited and additional rain will fall into the old and new snow cover, charging up the water column all over again.

    The danger is one or more of these storms will become strong enough to track well to the north. This would be a type of storm that brings in very moist, 50- to 60-degree air, combined with a couple of inches of rain. However, instead of that storm just bringing rain, snow and ice cover would melt rapidly, turning a moderate to heavy rainfall into an excessive monster unleashing the equivalent of 5 inches of rain or more in a matter of hours.

    We don't see one of these big, warm, north-tracking storms on the maps yet, but we do have multiple smaller storms that will add more snow and more water content to existing snow.

    All we can do is hope that as the season changes we continue to gradually lose the existing snow cover without big rain events. That way we would only have to deal with areas of isolated, more minor, typical spring flooding concerns.

    As a general rule, though, the longer you hold onto a deep snow cover into the spring, the greater the risk of a rapid meltdown and major flooding event.

    On Thursday, February 17, 2011, the National Weather Service got on board the flooding concern by issuing their assessment of the flooding risk for the North Central states. The Red River of the North, the upper part of the Mississippi River, and a part of the Missouri River are of concern.

    This can also occur from parts of the central Plains to the Ohio Valley and the mid-Atlantic if, say, one big storm were to swing through with heavy snow, followed by another big warm storm with heavy rain. At this stage, just about anybody from 35 degrees north latitude is fair game for snow well into March.

    The waters in Pittsburgh's three rivers rose to over 34 feet, flooding roadways and causing evacuations following the rapid meltdown of a deep snow cover combined with heavy rain over Pennsylvania and West Virginia during January of 1996. (AP Photo/Keith Srakocic)

    The overall pattern for the next six weeks or so will favor many storms with various tracks. It's a matter of placement and nature of these storms that will hold the key as to which areas get flooding and how serious that flooding will be, and whether it is caused by ice jams or not.

    We have begun to see some of the seasonal minor flooding issues surface in parts of the Midwest this week, due mostly to two recent heavy snowfalls that have melted in portions of Missouri and Illinois.

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