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Snowfall not expected to impact river levels

Published 12:10am Sunday, March 2, 2014

NATCHEZ — Even though significant snowfall remains on the ground in the northern United States, river forecasters say the Mississippi River will likely have a normal flood season this Spring.

National Weather Service Hydrologist Marty Pope said between 20 and 30 inches of snow are on the ground in northern Minnesota, with anywhere between two and 15 inches accumulated on the ground from the snowline at the northern Missouri border northward.

Another two to five inches remain in parts of northern Indiana, Ohio and western Pennsylvania.

“We have seen some snow melt in places, but then they get more snow,” Pope said. “It is not a bad picture, but we are really, right now, trying to keep an eye on everything up there. We are not getting a lot of increase or decrease in the snow.”

Immediate forecasts don’t foresee a rapid warm-up in the near future, and cold temperatures and more snow in some parts of the north are expected in the coming week.

The snow on the ground in northern Minnesota is the equivalent of four to six inches of liquid water, while the more southern snow is the equivalent of 2-4 inches.

That’s less than the snowmelt that preceded the unprecedented flood in 2011, Pope said.

“Snow melt will probably stay in place for a while, and there is not a lot of snow in the Ohio River basin right now,” he said. “If we do get some flooding on the lower part of the river, it will take some heavy rain across the (Ohio River) valley. The key will be, when that snowmelt comes, will we get some heavy rains at the same time?”

The 2011 flood, which reached 61.95 feet on the Natchez gauge, was precipitated by a 15- to 20-inch rain event in the Ohio River Valley at roughly the same time as the snowmelt. Flood stage at Natchez is 48 feet.

“The snowmelt didn’t do it itself (in 2011), but it did act as a good boost,” Pope said.

“For the (level of) snow were it is now, I think we will see more of an average year, with an average peak of 48-50 feet (on the gauge) at Cairo, Ill. We always watch the river there because all that has to come down here.”

The river saw a rise earlier this year due to an initial thaw, Pope said, but the year’s prolonged winter weather has pushed pause on the melt.

“As cold as it is, it is going to take things longer to get out,” he said.

According to the U.S. Army Corps of Engineers, the river is approximately two-and-a-half feet below its historic normal levels for this time of year. It is expected to stand at 31.9 feet on the gauge this morning.

The river’s high stage for the year thus far was 41.58 feet in early January, though it fell to approximately 23.5 feet by early February. The level rose to 36.23 feet by Feb. 18, but gradually fell toward the end of the month.