Cleanup efforts were nearing an end in parts of the Great Lakes region hit by lake-effect snowstorms that dropped more than a foot of snow over the weekend, but forecasters warned that another storm system could hit a few more later this week could add centimeters more snow.

Many school districts in western Pennsylvania remained closed Tuesday as storms finally eased after several days of lakeside snow that also fell on parts of western New York, Ohio and Michigan. These areas have had a foot (0.3 meters) or more of coverage over the past five days. More than 1.5 meters of snow had fallen east of Lake Ontario as of Monday, according to the National Weather Service.

Officials were making good progress in keeping roads open and most travel restrictions had been lifted Tuesday morning. However, motorists were still urged to slow down and be careful. Meanwhile, a winter storm warning was in effect for parts of western Pennsylvania, where a new storm could potentially drop 3 to 9 inches (8 to 23 centimeters) late Wednesday through Thursday morning.

Heavy snowfall in recent days has been responsible for a number of fatal accidents across the region.

According to the Iowa State Patrol, three people were killed in a crash in Iowa Monday morning after a driver crossed into the oncoming lane to pass a snow plow.

The accident occurred just before 9 a.m. in the 1700 block of Highway 1 south of Kalona. A 2002 Buick Park Avenue was traveling south on the highway behind a snow plow. The Buick crossed the northbound lane to pass the plow and collided head-on with a 2013 Nissan Rogue.

The drivers of both vehicles and the passenger of the Nissan were all killed in the impact. Another person was injured and taken to University of Iowa Hospitals and Clinics, according to the patrol’s accident report. The report did not specify the severity of the injuries or specify which vehicle the injured passenger was traveling in.