This past weekend saw calendars change from winter to spring, but for meteorologists, spring began March 1 as temperatures warm from the coldest months of the year.
No matter when one observes the changing of the seasons, it is also the time of the year in Wisconsin where flooding is at its highest risk.
Sarah Marquardt, Senior Service Hydrologist with the National Weather Service office in Sullivan, says flooding can happen anytime there is a heavy rain event, but there are several factors that lead to late winter and early spring having an elevated overall risk.
One deals with the remnants of winter. “That is the amount of snow, and then how fast that snow melts,” says Marquardt. “If that snow melts quickly, that can cause an increased risk for flooding.”
Another factor is the ground as it transitions from winter to spring. “A saturated ground means that that ground cannot absorb any more moisture, so that can lead to an elevated flood risk,” says Marquardt. “And then if the ground is frozen that can lead to an elevated flood risk because that water is not going to absorb into the ground, and it could cause more ponding and flooding.”
Throughout the year, the National Weather Service and the United States Geological Survey work together to monitor river levels, which includes issuing flood outlooks that are updated every few weeks.
Marquardt says as of mid-March, southern Wisconsin is at an average risk. That means a heavy rain event could cause flooding, but not due to other factors as was the case a few weeks ago thanks to snow storms in February leaving a deep snowpack.
“We had an above average risk at the end of February,” says Marquardt, “but we had a best-case scenario where we had a slow and steady snow melt during a period of dry weather. That really mitigated any flooding that could have occurred with that deep snowpack.”
Overall, Marquardt says the risk of flooding will always be possible whenever there is a heavy rain event, so caution and preparations are a best practice to follow to be ready for a flooding event.
Flooding is one of several severe weather threats that Wisconsin can see over the springtime, along with severe thunderstorms and tornadoes.
The National Weather Service needs the assistance of the public when it comes to reporting severe weather events and knowing what is happening in real time. That is why the Sullivan office is hosting its annual spring storm spotter training sessions in April and early May. Due to the pandemic, the sessions will be done virtually.
Warning Coordinator Meteorologist Tim Halbach spoke with WTMJ about what to expect with these sessions. Listen to the interview below.
