LEAD, S.D. - Residents of the northwestern Plains on Thursday started to dig out from this week's spring blizzard, which dumped up to 5 feet of snow, cut power and threatened to flood low-lying areas.

The heaviest snow was reported in the city of Lead in western South Dakota, near the Wyoming line, where the weather service reported 59.4 inches.

Crews struggling with the weight and volume of snow also had to find a place to put it after scooping it up, said Pat Milos, Lead's city administrator.

"There's nowhere to put it when there is this much of it," Milos said.

About 10 miles to the north in Spearfish, part of the roof at a Wal-Mart store collapsed Thursday afternoon, apparently under heavy snow. There were no reports of injuries.

Colder overnight temperatures, with lows in the high 20s to low 30s, could help lessen the flood threat by slowing the snow melt, said Col. Dan Mosteller, South Dakota Highway Patrol superintendent.

"It will give the snow a chance to soak in a little bit rather than running off," he said.

In southwestern North Dakota, the town of Bowman recorded about 18 inches of snow, the weather service said.

The potent storm in some areas knocked down trees and power poles. Wind gusting to 84 mph overturned a mobile home in the Nebraska Panhandle, and gusts to 71 mph were reported in eastern Montana, officials said.

The South Dakota Rural Electric Association reported about 2,000 power poles were downed, with trees knocked onto lines and many lines snapped.

More than 5,000 customers remained without power Thursday in the Dakotas.

State officials fully reopened Interstate 90 Thursday morning after clearing about 95 miles of the highway from Gillette, Wyo., to Spearfish, S.D. The road had been closed since early Wednesday.

Four deaths were blamed on the storm, including a utility worker who was electrocuted while working in near whiteout conditions Tuesday night in northwestern North Dakota, authorities said.

Ranchers were concerned about possible losses during calving and lambing season, said Kristi Turman, director of the South Dakota Office of Emergency Management.

"They're getting dug out and getting into their fields and checking their cattle," Turman said. "We don't have an exact number on losses."