After two consecutive years of heavy moisture, meteorologists are very certain that flooding will be a part of 2020.
How bad it gets will depend on a number of factors that will be set in motion over the next couple of months.
Mike Gillispie, service hydrologist for the National Weather Service in Sioux Falls, told the Press & Dakotan Wednesday that flooding is almost an inevitability in southeast South Dakota this spring.
“Looking at river levels, water table levels, the soil moisture levels — everything is pretty much as wet or wetter than it has ever been at this time of year,” Gillispie said. “Even if we only see normal precipitation for the next several months, we’re going to have above-normal flooding because of how wet things are.”
Flooding carrying over from 2019 is ongoing in some parts of southeast South Dakota as the winter progresses.
“We are still looking at minor to moderate flooding along the entire James River down through Mitchell, at least,” Gillispie said.
He said that the Yankton and Scotland gauges are below flood stage, though many areas along the river in Yankton County — especially around the Highway 81 and Highway 46 crossings — have standing water on either side of the river banks that has been frozen in.
Gillispie added that there’s also a pocket of flooding along the Missouri River in the region.
“We do have a bit of minor flooding going on between Ft. Randall and Lewis & Clark Lake,” he said. “(At) Gavins Point, the releases are higher than normal, but we’re not seeing any flooding downstream … at this time.”
How bad flooding gets this spring is largely going to depend on what gets added to the moisture already present, Gillispie said.
“The biggest thing is going to be how much snowpack we build up over the next, say, about two months or so into early spring,” he said. “Right now, the snowpack is not terribly bad, particularly south of I-90. There’s not a whole lot of snow.”
Snowpack conditions to the south of I-90 in southeast South Dakota run from around 4-10 inches of snowpack while north of I-90, it’s around 15-20 inches.
“There’s some water sitting out there, but the big factor going forward is how much additional water we add to that snowpack that’s out there,” Gillispie said. “And of course, as we get closer to late February and March, how fast is that snowpack going to melt and how much additional rain do we get?”
Gillispie said that, while flooding is expected to some degree, there is one scenario that would be close to ideal for the region.
“The best-case scenario would be we don’t get much additional snowfall and we have some warmer-than-normal temperatures through the rest of winter into the early spring that melt that snowpack off slowly over a four- to five-week period, as opposed to a fast warm up when we get into March,” he said.
In the short term, he said that some of that is in the forecast.
“The next couple of weeks looks like we’re probably going to be on the warmer side,” he said. “There’s not any big threat of a lot of cold air coming back in again — at least into early February. Precipitation right now looks pretty close to normal.”
However, he said that longer-term outlooks still point towards below-normal temperatures in the next couple of months with precipitation largely hovering around normal.
Gillispie said that now is the time to prepare for spring flooding issues.
“Hopefully, we’re not going to see the kind of record flooding we saw last year,” he said. “But the fact that we’re starting out so wet and the rivers are starting out so high, even normal precipitation is going to give us worse-than-normal flooding this spring. If you had issues with anything flooding that is movable that you can move to higher ground, that kind of thing you can do.”
He added that it’s also the time of year to look into flood insurance.
“If you’re not flooded right now, look into flood insurance,” he said. “You have to have that policy in place for 30 days through the National Flood Insurance Program.”
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