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Why does the river forecast keep jumping higher?

Moderate flood stage expected tonight
Flood Warning for Ohio River starting Monday
Posted at 8:43 AM, Mar 03, 2021

Have you noticed how much the river crest projection has changed this week?

Monday we were talking about a crest of 53.2 feet. Yesterday it was raised to 54.5 feet and now today we are expecting a crest of 56 feet. That crest is expected to happen late Wednesday night and puts Cincinnati at moderate flood stage.

The change in forecast piqued the interest of those at WCPO 9, so we made some calls to the National Weather Service office in Wilmington, Ohio, to get a better idea if this is normal. After all, we did see record-setting rain on Sunday and substantial snowmelt.

“Our smaller rivers and streams are much easier to predict the rise and fall, because it’s just rainfall and runoff into that specific area that goes into the forecast,” says Meteorologist Logan Clark. “But with the Ohio River, what makes it so challenging is you have the rain to consider plus the volume of water coming from all the other creeks, streams and rivers.” The Ohio River is basically the bottom point of water drainage locally.

The bigger the river, the bigger the magnitude. And we have a whopper in our backyard, so to speak.

I specifically asked about the reliability of these river products and the forecaster I spoke to said these adjustments in the river crest are very normal.

“The closer we get to the crest, the more accurate the forecast becomes,” said Clark.

It’s kind of like making a weather forecast 5 to 7 days out. We have a ballpark idea of where temperatures should end up and the timing of rainfall. But as you get to 24 to 48 hours from the event, those details become much clearer and more reliable.

“24 to 48 hours brings more confidence. You can look at the gauges upstream and what the river flow going into is like,” said Clark about the river forecast.

Speaking of that forecast, the latest will be coming out before the noon hour, giving us another update on the expected crest tonight, but it shouldn’t change too much.