The likelihood of major flooding in Missouri and Illinois is especially high this spring.
The National Weather Service on Friday released its report forecasting flooding for eastern Missouri and areas in southern Illinois. Its author, hydrologist Mark Fuchs, said parts of the Mississippi River are facing a 50 percent probability of hazardous flooding.
"All points north of Winfield, and including Winfield, are looking at probabilities we have not seen, really ever,” he said.
The outlook is based on upstream snowpack in the Mississippi, Missouri and Illinois river basins, along with the current streamflows and soil moisture in the area.
Since Christmas Eve, the St. Louis area has had at least three inches above normal precipitation, with higher levels south of the city, according to Fuchs. That’s led to above-normal soil moisture and stream flow. And he said with temperatures expected to become colder later this week, snow in upland regions won’t melt anytime soon.
“That will increase the probability of significant flooding, because the snowpack won’t melt gradually — at least for awhile,” he said.
When the temperatures heat up in the spring, it will cause high altitude snow to melt rapidly, he said. As a result, the quick release of water from the build up could cause historic flooding in Missouri and Illinois.
The Illinois, Missouri and Mississippi rivers are facing the likelihood of moderate to major flooding, Fuchs said. According to current projections, the Missouri River could see moderate flooding at Jefferson City, Hermann and St. Charles. Along the Mississippi River, major flooding could occur at Saverton, Clarksville and Chester.
Fuchs said he has never seen higher flood levels projected since his organization began publishing the report more than a decade ago.
Still, he said, major flooding could be avoided if upstream snow melts more gradually in the coming months. There is also a possibility Missouri and Illinois could get less rain this year than normal, he said.
Fuchs said the Climate Prediction Center’s three-month projections on the region’s precipitation, released on Thursday, shows there will likely be “below-normal precipitation” in St. Louis. That expectation is based on El Niño, a large-scale atmospheric pattern that develops from warming in the central and eastern Pacific Ocean.
But Fuchs said there are problems with basing forecasts on the occurrence of an El Niño.
“Given that this is just barely an El Niño to begin with, and that it was only classified as an El Niño in the last few weeks, leaves one to believe you really shouldn’t put a whole lot of faith in the probability of both the temperature and the precipitation patterns working out to be a classic El Niño signature,” he said.
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