Ice jams on the Mississippi River and Elk River are causing some flooding problems in the city of Elk River, the National Weather Service said Wednesday, and it could get worse.

Flooding in the winter? Perhaps a little unusual, but yes, said Eric Ahasic, a meteorologist with the NWS.

Ice jams happen when shallower areas of rivers freeze faster than deeper areas and the ice gets stuck where the rivers curve and curl. Water continues to flow downstream, but when it is blocked by the ice jams, also called ice dams, it has to go somewhere, Ahasic said. That means it overflows the banks and floods.

Ice jams are perfectly normal and don't usually cause flooding, but large amounts of rain this year plus abnormally high temperatures throughout November and the first week of December are what's causing the flooding problems.

No roads are closed in Elk River — yet. But the Sherburne County Sheriff's Office said several roads are being affected, including Yankton Street, Waco Street and 189th Avenue, as well as Wapiti Park.

The NWS has issued a flood warning for Sherburne and Wright counties, particularly in the low-lying areas near the rivers. The warning was expected to expire at noon Thursday, but with an inch of rain in the forecast and the river still rising, it could be extended, Ahasic said. Snow melt caused by the rain won't help.

The mild temperatures of the past two days, which are expected to continue into the weekend, could help or hurt.

"Definitely the rate it has been freezing up has slowed," Ahasic said. "But we'll have temps below freezing at night, so [the ice dams] won't really be going anywhere. They can usually take awhile to break up and move out."

Flooding from ice jams is notoriously difficult to forecast, Ahasic said.

The flowing water will eventually break up the ice dams and move them downstream, he said. But until then, it could be "a mess," he said.

Elk River's Fire Department said residents can pick up sandbags at City Hall weekdays between 8 a.m. and 4:30 p.m. You need to show photo ID. The first 50 sandbags are free, but more can be purchased. People in other cities should contact their local city hall or fire department.