Updated: 4:48 p.m.
Localized, torrential rain sparked flash flooding in parts of Duluth late Monday night, swamping streets and the Interstate 35 tunnels near the shore of Lake Superior.
The National Weather Service reported radar estimates of 3 to 6 inches of rain over downtown Duluth, the Hillside and near the College of St. Scholastica in just a few hours.
Video posted to social media showed cars sitting in water nearly to the floor of their passenger compartments, and a cascade of floodwater flowing down streets near Whole Foods Co-op on the Duluth Hillside, where a larger flash flood in 2012 damaged streets and storm sewers.
In downtown Duluth, part of Superior Street was closed Tuesday morning at First Avenue East after the heavy rain washed gravel and dirt from a construction zone onto the main thoroughfare. Superior Street is reopened as of Tuesday afternoon.
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The city said the heavy rain caused “significant erosion” in the First Avenue East work zone, washing out about 1,000 cubic yards of material.
“The contractor is working as quickly as possible to remove the material and to reopen Superior Street. The road is expected to reopen by the end of the day,” the city reported.
Assessment of the damage to the project was underway, but the city said it expected the damage would delay the reopening of First Avenue East.
There were no updates on possible flood damage to buildings early Tuesday, and no immediate reports of injuries. The city of Duluth advised drivers to “use caution as some manhole covers need to be reset and debris cleanup is underway.”
Minnesota Department of Transportation traffic cameras showed traffic stalled amid flooding in the I-35 tunnels near downtown just after 10 p.m. Monday. The Weather Service reported the freeway was closed for a time due to the flooding; the freeway was back open Tuesday morning.
“The heaviest rain was just over one or two creek basins in the city. And so it was all concentrated in a really small area that just could not be handled. So it started to run out into roads,” National Weather Service meteorologist Ketzel Levens said Tuesday morning. “I think some of the water that ended up being in the tunnels was actually from water that was flowing down the streets on the Duluth Hillside and then going over the edge and into the tunnels.”
“We are only just now starting to get some observations in,” Levens said, “but we got anywhere — in a very, very localized area in Duluth yesterday — from three to possibly even six inches of rain within only about two, three hours.”
The Duluth airport, just a few miles away, saw much less rain Monday night — just over an inch.
After a break overnight, more rain showers were falling Tuesday morning in northeast Minnesota. Rain was expected to continue before tapering off into drizzle early in the afternoon.