Flooding Looms From Midwest to Northeast

(March 10) -- The combination of melting snow and rain from a complex, slow-moving storm has set the stage for flooding along many rivers and streams from the Midwest to the Northeast through this weekend. The most serious threat will likely be in western Pennsylvania, western Maryland and West Virginia.

The Army Corp of Engineers in Pittsburgh said Tuesday its 16 reservoirs have been drawn down because of rain and melting snow. Flood watches have been issued by the National Weather Service. Major rivers in the region include the Allegheny, Monongahela and Ohio.

While scattered showers are expected through Thursday, bands of heavier rain and isolated heavy thunderstorms are forecast from Thursday night through Sunday. Rainfalls of 1 to 3 inches are possible, with locally higher amounts a risk, depending on the path of the storm. A melting snow pack is adding to the threat.

Melting snow and rain has set the stage for flooding along many rivers and streams from the Midwest to the Northeast

AP Photo/Ross D. Franklin

Melting snow and rain storms are making a mess in several parts of the nation. Here, heavy rain has left the usually dry Salt River in Phoenix swollen to the point of flooding several roads Monday.

Snow levels in lower elevations hold the equivalent of 1 to 4 inches of rain, and it's likely that all of this snow will melt because of temperatures expected in the 50s and lower 60s by the weekend. This could double the amount of water being added to the river system by the rain. Rivers are already swollen because of melting snow.

The snowpack in higher elevations, after a snowy winter, holds as much as 12 inches of water, with most areas having at least 6 inches. Much of this snow will also melt, so regardless of the amount of rain associated with the storm, a tremendous amount of water will be added to the rivers from melting snow.

Parts of Nebraska, Iowa and Illinois are already flooded, and the potential for flooding will have to be monitored across the remainder of the mid-Atlantic region and New England as the storm moves eastward.

New England and New York state will have heavy rain at times over the weekend, and interior areas still have a deep snowpack. With the snow in many locations from upstate New York through interior New England holding more than 6 inches of water, the rain will fall as the snow melts.

Fortunately, recent warm weather has allowed much of the snow from Philadelphia to Washington, D.C., to melt slowly enough to prevent flooding problems. As a result, severe flooding is unlikely. However, the ground is saturated and rivers are higher than normal, so heavy rain associated with the storm could cause some flooding, mainly in urban areas or along small streams.