AccuWeather.com

By Alex Sosnowski, Expert Senior Meteorologist

Mar 19, 2010; 8:13 AM ET

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As some rivers hold near record levels and others rise markedly over the northern Plains this weekend, many communities in the region could be in for a long battle with flooding for weeks to come.

Surging temperatures during the first part of the week accelerated snowmelt over the Dakotas, western Minnesota and northwestern Iowa.

New Weather Impacts

While the massive snowpack over the northern Plains has shrunk substantially, there are still hundreds of square miles where the snow contains from 4 to 8 inches of water.

AccuWeather.com meteorologists remain concerned that despite the colder weather moving in now, future thaw cycles, combined with additional expected storms with rain and eventual runoff from new snow over as many weeks, will prolong flooding in some communities and lead to new flooding in others.

The storm affecting the central Rockies and Plains into the weekend will miss much of the area experiencing the worst flooding. However, some snow will fall and melt over portions of flooded Iowa.

The prediction of exact river levels in the immediate area and downstream locations in the weeks ahead are very complex and uncertain.

Because of its size and massive watershed, the central and lower Mississippi River from Missouri and Illinois on south could remain above flood stage for months. The river was just beginning it rise in the Deep South this week.

The Situation Now

Some rivers, such as Red River of the North, will remain at or above flood stage for weeks. Generally the larger the river, the longer the flooding cycle.

There have never been back-to-back years with flooding of this magnitude along the Red River in its 110-year history according to National Oceanic and Atmospheric Administration hydrologists.

The Little Sioux River at Spencer, Iowa taken this week by AccuWeather.com Facebook user Paul Andrew Stanzel.

Residents and officials in Fargo and other communities hope that levees hold for the long haul.

At Fargo, the Red River will come within a few feet of the record mark of 40.8 feet set just last year. The river is forecast by the National Weather Service to crest near 37.5 feet on Sunday.

The Red River of the North, which flows from south to north, will rise significantly to major flood levels above Fargo into Manitoba, Canada in the weekend and beyond.

Portions of the James (of the northern Plains) and Little Sioux rivers have set record levels this week.

The Des Moines and Raccoon rivers around Des Moines have been cresting at moderate to major flooding levels late this week. It could be days before the rivers fall below flood stage.

In areas where there is still substantial snow on the ground, such as much of North Dakota and northern South Dakota, ice jams can lead to rapid rises on area streams and rivers. Farther south, this danger has passed.

Agricultural Impacts

In addition to the threat on individual communities, some unprotected agricultural areas will be under water for weeks.

The flooding is taking place much earlier that what typically occurs. The flooding cycles could run their course, perhaps allowing the ground to dry out in time for the corn and wheat planting season.