The worst of the spring flooding in Minnesota is yet to come, but warming temperatures with highs in the 40s and 50s over the next week will melt away snow and lift frost from the ground in what will pave the way to the main event, so to speak.
There isn't an exact date for when the rivers will begin to reach flood stage, but Craig Schmidt, a service hydrologist with the National Weather Service, is closely monitoring the situation and expects things to ramp up within the next week.
"I think we'll start seeing that as we get into this coming weekend," Schmidt said. "As we get to Friday, Saturday, Sunday and Monday, we are going to warm up even more and we'll see temperatures into the 50s. Our lows are not going to get to freezing and we'll see everything start to move pretty quickly at that point."
Basically, a lot of the snow that has melted has ponded in fields. Once the frost is out of the ground, the water will start migrating into waterways, leading to rising rivers.
"Once the soil thaws out then it starts moving through the groundwater into rivers," says Schmidt.
In advance of the expected melt, the National Weather Service has issued new flood warnings for the following river areas:
- Minnesota River at Morton affecting Renville County
- South Fork Crow River below Mayer affecting Carver County
- Mississippi River at St. Paul affecting Dakota, Ramsey and Washington counties
- Mississippi River near Hastings affecting Dakota, Washington and Pierce counties
For the Mississippi River at St. Paul, the river level at 10 a.m. Tuesday was 6.4 feet with the level expected to rise above the flood stage of 14 feet this weekend and continue to rise next week.
At 17.5 feet, Harriet Island begins to submerge.
Extreme flooding in Nebraska not a preview for MN
Extreme flooding has been the talk of the country since last week's major storm system delivered heavy rain, high winds and snow from the Texas panhandle up through Colorado, Kansas Nebraska, the Dakotas and Minnesota.
Nebraska was hit hardest with historic flash flooding that has swallowed towns and washed away roads.
The chances of similar flooding in Minnesota is unlikely, but not impossible.
"It's an outside chance," says Schmidt. "What happened in Nebraska was their snowpack was already ready to go. It was right at the period where it was all ready to melt and run, then they added 2-3 inches of really heavy rain on top of it at just the wrong time. It was a catastrophic event."
Fortunately, the snowpack in Minnesota has been allowed to melt at a normal pace over the last week, and there's no significant rain in the forecast.
"If we were to get 3 inches of rain next Sunday or something, right as we're about to get everything moving into the rivers, we could see another catastrophic event but we don't see that in the forecast at this point," Schmidt explained.
Although catastrophic flooding isn't expected, major flooding is likely in many river areas, among them the Minnesota, Mississippi and Cottonwood, not to mention the Red River Valley in and around Fargo-Moorhead and Grand Forks.
Worst flooding could be along the Minnesota River
"There's an awful lot of water just waiting to get in that river, and that has to flow up through the southern Twin Cities before it meets the Mississippi in St. Paul. We're going to get quite a lot of that and there will be flooding for sure," says climatologist Kenny Blumenfeld, who discussed the spring flood threat in detail in this week's episode of the Way Over Our Heads podcast with Jim du Bois.
Schmidt is also watching the Minnesota River closely.
"The Minnesota has a very good chance of hitting a number of major flood levels," said Schmidt. "I think we'll have decent flooding on the Mississippi, but not catastrophic."
Major flooding occurs when river rises begin to affect state or federal highways, the "stuff beyond your dirt and county roads," according to Schmidt.
The National Weather Service works in cooperation with local emergency management and cities to determine what major flooding is at any given location.
"In any one place it's hard to say exactly what's going to happen," says Blumenfeld. "There's going to be flooding. We're talking about river flooding, not the entire state going under water."
Note: Blumenfeld will be on stage at Bryant Lake Bowl in Minneapolis as he discusses the nuances of Minnesota's changing climate and the wildest things he's heard over the years. The show is March 28 at 7 p.m.