GRAND FORKS — The risk for significant flooding in much of the Red River Valley this spring has increased after recent winter storms dumped more than a foot of snow in some southeastern North Dakota cities.
On Thursday, March 9, the National Weather Service office in Grand Forks issued an updated flood outlook for the Red River Basin. The outlook shows an increased risk of significant flooding, which is defined as moderate or higher flooding, in the Red River Valley and along its tributaries since the last outlook was issued on Feb. 27. The most severe flooding is expected on the Red River in Fargo and Sheyenne River in Harwood, North Dakota.
The outlook is based on observed conditions through March 6, and takes into account forecast precipitation through Monday, March 13, which includes the widespread system expected to move through the Red River Valley over the weekend.
While the northern valley avoided most of the snow in the weeks since the last outlook, Fargo and surrounding areas received heavy snowfall. Amanda Lee, NWS service hydrologist, outlined what that means for the southern valley and upstream cities in a webinar on Thursday.
“The south did see a few systems move through and drop some snowfall, bringing their total for the time period, this last two weeks, up to 20-ish inches above normal snowfall in that time period for the far south, with lesser amounts as you move north in the basin,” said Lee.
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The updated flood outlook says North Dakota cities like Wahpeton, Grand Forks, Oslo, Drayton and Pembina have a 50% chance of moderate flooding, while the Red River in Fargo and the Sheyenne River in Harwood both have a 50% chance of major flooding. In southeast North Dakota, moderate flooding is projected for tributaries of the Red River, like the Maple River in Enderlin and Mapleton.
Previously, the NWS had projected minor flooding for much of the Red River Basin, with moderate flooding in Fargo, Oslo and Pembina in a Feb. 27 flood outlook.
Lee also gave the flood outlook for the Devils Lake Basin. She said there is a "good chance" of a rise of 1-2 feet in Devils Lake in the early summer.
In the coming weeks, a number of factors will determine if the risk of spring flooding increases or decreases.
“The snowmelt timing and how the thaw cycle shakes out, along with any additional snow or rain that we will see in the coming weeks will be the most important factors as we head into the spring flood risk,” said Lee.
The NWS says the system moving into the region on Saturday and Sunday has the potential to drop four inches or more on most of eastern North Dakota and northwestern Minnesota, with an even greater snowfall potential in northeastern North Dakota. Through mid- to late-March, the region may get less precipitation, but colder than normal temperatures are expected to continue.
“Probabilities are looking better and better for a more of a delayed melt this year, pushing more into the April timeframe before we start warming up a little bit,” said Lee.
The later the melt, said Lee, the greater the risk is for significant flooding.
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Because colder than normal temperatures are expected to continue through March, the NWS plans to issue another flood outlook in two weeks on Thursday, March 23.
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