OKLAHOMA CITY (AP) — The death toll rose to six today from winter storms in the U.S. midsection that pushed toward the Northeast. More than 600 flights were cancelled in the storm's path. Two passengers in a car on a sleet-slickened Arkansas highway died when the vehicle crossed the center line and struck an SUV. In Oklahoma, the Highway Patrol said a 76-year-old woman died yesterday when a truck crossed into oncoming traffic and hit the car she was in. The Highway Patrol earlier reported that a 28-year-old woman was killed in another crash. The storm's winds were also blamed for toppling a tree onto a truck in Texas, killing the driver, and a tree onto a house in Louisiana, killing a man. More than 600 flights nationwide had been cancelled by near midday Wednesday, according to flight tracking site FlightAware.com. More cancelations were likely, with Washington, New York and Philadelphia expected to see the most problems. Blizzard conditions were possible today for parts of Illinois, Indiana and Kentucky. Thirty-four tornadoes were reported in Texas, Louisiana, Mississippi and Alabama during yesterday's outbreak, the National Weather Service said. The storms left more than 100,000 in the region without power for a while, darkening Christmas celebrations.