Unseasonably warm temperatures this weekend following polar vortex could cause flooding, Madison mayor warns

February 2, 2019

Just days after a polar vortex plunged temperatures to minus 26 degrees in Madison, drastically warmer temperatures could cause a new host of problems for the city.

The quick swing in temperatures could bring new water main breaks, flooded streets and crumbling roads, Mayor Paul Soglin said.

Madison and much of the Midwest bundled in several layers of clothing, took shelter indoors at every possible moment and lamented the bone-chilling cold throughout the week, but unseasonably warm temperatures were right around the corner with the National Weather Service forecasting highs in the mid-40s for Sunday and Monday. Fog, drizzle and possible rain will accompany the warmer weather.

“So now we go from the freezer into the swimming pool,” Soglin said.

With above-freezing temperatures, the snow blanketing Madison yards and piled high along curbs will begin to melt. Some may see that as a blessing, but Soglin and Steve Schultz, assistant Streets Division superintendent, said there is a potential for flooding along with that melt.

More than 15 inches of snow fell in Madison last month. That snow and ice could be blocking some of the approximately 20,000 drains that lead from city streets into the storm sewer, Soglin said. As the snow melts, the resulting water could pool on streets if it can’t reach the drains.

“We have a lot of snow out there,” Schultz said. “It’s going to take a little bit of time for this to warm up and melt, so it’s not going to be an all-at-once big rush to the inlet.”

Engineering staff have been clearing inlets to storm drains throughout the week, particularly in low-lying areas of the city, Deputy Mayor Katie Crawley said.

Residents are asked to call the city’s engineering operations at 266-4430 if they see flooded streets. They can also help clear access to storm drain inlets by breaking up snow and ice that are blocking them.

Melting snow

Soglin said the hope is that the melted snow will run underneath the snow piles on curbs into the inlet and be mostly unseen. Because the low temperatures will remain above freezing throughout the weekend, water should continue to flow through the drains overnight, preventing new ice blockages from forming.

The melting snow will not pose a threat to water levels in lakes Mendota, Monona, Waubesa and Kegonsa, said John Reimer, assistant director of the Dane County Land and Water Resources Department. There hasn’t been enough snowfall to significantly affect the volume of water in the system.

Melting ice and snow could also affect residential properties, Soglin said. Gutters and downspouts could be blocked with ice that should be broken up, and downspouts should also be draining away from the home. Melting snow could also affect homes with basements prone to flooding.

The thawing ground could also cause problems for water lines, Soglin said. The fluctuating temperature and the freezing and unfreezing can put stress on the pipes.

“The water utility does something that none of us would dream of doing, and that’s to work with flowing water in 20-below degree weather,” Soglin said. “They will continue to deal with changes to the system as we see the impact of temperatures changing.”

Shock absorbing

Potholes are another potential problem, he said. Many potholes are caused by water that has run into cracks or small holes in the road’s surface, and when that water freezes, it expands and breaks the pavement apart.

Aside from potholes, Schultz said Madison streets are in “great winter driving conditions” and that the Streets Division will continue to monitor the streets and clear the slush that forms in the roadways through the weekend.

“The Monday morning commute should be much better than it has been for several weeks,” Schultz said.

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