Will Heavy Winter Snow Increase Spring Flood Threat Across Northland?

This winter, when in doubt, just predict snow. Chances are you'll be right. Duluth has picked up over 75" of snow during the first half of winter. That is more than 28" of snow above average, and 27"+ snowier than last winter on this date. Snow lovers are thrilled. Commuters? Not so much.

According to NOAA's National Operational Hydrologic Remote Sensing Center (NOHRSS) there is 12 to 30" of snow on the ground across the Northland, with the heaviest amounts near Lake Superior. Thank you lake-effect snow bands. And there is a LOT of liquid water trapped in that impressive canopy of snow.

Here is an NOAA NOHRSS derived product estimating the amount of liquid water tied up in the snowpack across the Northland: a large area of 6-8" with closer to 10-12" of liquid water near Lutsen. Stating the obvious: that is plenty of water locked up in a frozen state.

The reality: it's early to be talking about spring flooding, and the National Weather Service will have updates as we get into February and March. Hydrology (river forecasting) is a science within the science of meteorology, and I defer to hydrologists who have been doing this for decades. There are many factors in play:

Yale Climate Connections has a timely graphic (above) that shows some of these factors in play, including depth of ground frost, the amount of water locked up in the snowpack ("snow water equivalent), saturated soil, and additional snow and rain as we come out of winter. We don't know what we don't know.

Even thought we may wind up with close to 100" of snow in Duluth-Superior, a slow thaw may prevent widespread spring flooding on area rivers and streams. Soil moisture was relatively low heading into winter, and that helps our cause.

A worst-case spring flooding scenario would be:

- Rapid thaw with quick warming into the 40s and 50s.

- Heavy rain falling on top of our snowpack.

- Additional heavy snow into March and April.

Some of these factors are unknowable at the present time. But what may be one of the snowiest winters in a generation may prime the pump, increasing the potential for flooding problems later this spring. If you've experienced spring flooding in the past, you'll want to stay alert and stay up on the latest advisories from NOAA's Duluth National Weather Service in the months to come. We'll keep you posted right here at KOOL1017.