SIOUX FALLS, S.D. (AP) — Another spring day brought yet another snowstorm to the Dakotas on Thursday.

The National Weather Service posted a winter storm warning and winter weather advisories for far eastern South Dakota, where half a foot of snow or more could fall. It also forecast several inches of snow along strong winds for southeastern North Dakota.

Snowstorms have been crossing the Dakotas for more than a week, dumping record amounts of snow in some areas. Eastern South Dakota is still recovering from a three-day snow and ice storm last week that knocked out electricity to nearly 100,000 people and downed or damaged thousands of trees.

Officials in Sioux Falls said Thursday’s snowfall could set back a massive cleanup effort. Hundreds of people are working to clear trees and branches over an area spanning more than 70 square miles.

“As we continue to find the best way to do this operation, we are also backing that up with the right amount of personnel and equipment,” Public Works Director Mark Cotter told the Argus Leader newspaper.

However, some city and state crews were taken off the streets Wednesday to prepare for snow removal Thursday, Cotter said.

In western North Dakota on Wednesday, slick conditions on state Highway 22 in Dunn County led to a series of vehicle crashes involving 13 people. There were no serious injuries, but it took crews three hours to clear the area, Highway Patrol Sgt. Dan Haugen told The Dickinson Press.

“People were driving too fast for the conditions,” Haugen said. “They weren’t leaving enough space between other vehicles, and these crashes could have been preventable with some more defensive driving.”

Numerous crashes also were reported in southeastern North Dakota early Thursday, according to KFGO radio in Fargo.

The recent snowfall has increased fears of flooding in the Fargo area. Officials on Thursday reopened Sandbag Central, where volunteers are filling sandbags to hold back the expected floodwaters.

The city wants an additional 500,000 sandbags, to go with the 1 million bags that were made in early April and 300,000 bags left over from the 2011 flood. City officials originally were planning for a 38-foot Red River crest, which is 20 feet above flood stage. That has now been bumped to 41 feet because of the above-normal precipitation.

The western South Dakota city of Rapid City also has seen above-normal precipitation recently, with record amounts of snow on both April 9 and on Tuesday. However, heavy amounts of snow forecast for Wednesday didn’t materialize, leading some parents to criticize a decision by school officials to call off classes for the day.

The decision was influenced by a winter storm warning for the area, Superintendent Tim Mitchell told the Rapid City Journal.

“Last week the weatherman was right, and this week the weatherman was wrong,” he said. “Certainly in hindsight you think back and we potentially could have had school, but when I was on my way to school this morning the roads were very icy and if someone had an accident it would have been bad.”