The weekend storms have left thousands of Chicago area residents dealing with power outages, property damage and traffic snarls -- and more dangerous weather is on the way.

The National Weather Service has issued a tornado watch for northern Illinois -- including Cook, DeKalb, DuPage, Kankakee, Lake, McHenry and Will counties -- that will remain in effect until 1 a.m. Monday.

Additionally, approaching storms have prompted a lakeshore flood warning that will remain in effect until 9 p.m. because a two-foot drop in Lake Michigan water near Chicago indicates a seiche is in progress across the southern parts of the lake, causing water levels to fluctuate rapidly.

Residents on or near the shore should be alert for rising water and evacuate docks, piers and breakwalls immediately, the weather service said.

A flash flood watch also remains in effect for northern Illinois until Monday night. A flash flood watch means conditions may develop that lead to flash flooding. Residents should be prepared to take action, the weather service said.

The National Weather Service is predicting an 80 percent chance of storms Sunday evening, when temperatures will be about 82 degrees.

The storms are expected to continue into Monday morning, and could be severe with damaging winds and heavy rain, the national weather service said.

After Sunday's storm, 46,000 Commonwealth Edison customers are without power as of 2:30 p.m., utility spokeswoman Judy Rader said. The outages have affected 6,000 Chicago customers, while 20,000 south suburban, 14,000 west suburban and 6,000 north suburban customers are without power. The numbers include the 11,500 south suburban customers still without power from Saturday's storm.

The city's Department of Streets and Sanitation is cleaning up "light to moderate" damage from Sunday's storms, according to a Streets and Sanitation release.

As of 8 p.m., crews have responded to 249 "tree emergencies," including a tree that fell on a car in the 400 block of West 37th Street, according to the department, which stressed most of the tree damage involved downed branches.

The department has also responded to 35 traffic light outages, 15 damaged light poles and 34 downed city wires, the release said.

On the roads, Saturday's tornado still has Interstate 57 closed, State Police said Sunday afternoon. Five transmission towers that supported high-voltage power lines were "severely damaged" by the storm and left stray wires blocking the expressway. ComEd experts say transmission tower damage is "rare" and may take up to a week to fully repair.

The interstate remains closed in both directions Sunday afternoon and may not be open Monday morning, said Illinois State Police District Joliet Sgt. Martez Malone. Traffic was "moving slowly" Sunday afternoon, and State Police expect even heavier congestion Monday morning, he said.

"Last I heard, there is a possibility it will reopen tomorrow [Monday] afternoon, but we can't be sure," Malone said.

State Police are detouring southbound vehicles between Sauk Trail and Route 17 -- about four miles -- before reentering the interstate near Monee Road, Malone said.

Northbound traffic is closed at Route 17 and is being diverted to Route 30, I-394 or I-80, Malone said.