By CNN Staff
(CNN) -- A major blizzard that has hammered the Midwest, prompting road closures, school cancellations and power outages, is expected to weaken Friday.
"The blizzard and heavy snows affecting the Midwest into the Great Lakes will continue throughout the evening hours of Thursday and finally begin to wind down by Friday," the National Weather Service said.
But still light snowfall is expected to continue in a large swath of area from the Ohio Valley to New England, forecasters said.
The severe weather caused problems in many areas in the past few days.
Blinding snow also is blamed for a 30-car pileup on Interstate 35 near Fort Dodge, Iowa. Two people died, including a 43-year-old Arkansas woman, Sgt. Scott Bright of the Iowa State Patrol said Wednesday.
At least 20,000 customers were without power in Iowa early Friday, most of them in the Des Moines area, according to MidAmerican Energy.
The storm -- the first blizzard of the season -- made travel treacherous throughout the region. Nebraska authorities temporarily closed much of snow-packed Interstate 80 through the state Thursday as blowing snow dangerously reduced visibility. The interstate was reopened later.
But motorists were advised to be cautious.
Things were not much better in Iowa, Bright said.
"When the winds start to blow, you can see about 5 feet in front of your vehicle" he said. "We've had major issues all over the place. We got around 10 to 12 inches throughout the state and it's a wet snow. We have around an inch of ice on our roadways."
Close to 100 accidents had been reported in Iowa by late Thursday morning, Bright said.
In Wisconsin, Gov. Scott Walker declared a state of emergency, put the National Guard and state patrol on standby and closed state offices to the public in 20 counties most likely to be affected by the storm. Employees were still expected to report for work.
As much as 7 inches was already on the ground Thursday in parts of southern Wisconsin.
The Wisconsin State Patrol and National Weather Service urged people to avoid traveling.
CNN's Stefan Simons, Jim Kavanagh, Jareen Imam, Laura Smith-Spark, Carma Hassan and Joe Sutton contributed to this report.