An unexpected winter storm that struck North Texas before daybreak Tuesday put morning commuters on ice, cancelled flights and forced some schools to open later than normal.Forecasters had predicted a slight chance of light sleet but had said that most of the precipitation should stay southeast of Dallas-Fort Worth.Oops.Its always a challenge to predict winter precipitation in North Texas, said Nick Hampshire, a meteorologist with the National Weather Service office in Fort Worth. Its always a fine line. If it had been two or three degrees warmer, we would have been talking about a rain event. Many parts of Tarrant County received as much as a half-inch of sleet and snow, the most significant icy precipitation since the Christmas Day storm.But dont expect a repeat Wednesday morning. Promise, the weather service said. The day will dawn chilly, with temperatures in the mid 20s, but the forecast high is about 50 degrees, and there is no chance of precipitation.Temperatures should warm into the upper 50s by the weekend before another cold front arrives in time for Mondays Martin Luther King Jr. Day holiday.Early Tuesday, the surprising sounds of thunder and sleet caught residents unaware.Streets and overpasses began icing up during the 5 oclock hour. Five hours later, Fort Worth police had reported more than 40 accidents. Dozens of other wrecks were reported throughout Tarrant County.A few overpasses, ramps and bridges, including the Hulen Street Bridge in west Fort Worth, were also closed for a time because of ice.Some businesses and school districts also delayed their openings.At Dallas-Fort Worth Airport, 343 American and American Eagle inbound and outbound flights were cancelled Tuesday morning.American Airlines spokesman Matt Miller said operations returned to normal by lunchtime but said some flights were canceled Tuesday afternoon.A Southwest Airlines spokeswoman said that there were 26 flight cancellations at Dallas Love Field but that operations returned to normal by 10 a.m.Many areas of Tarrant received about a half-inch of snow and sleet, while parts of Denton and Collin counties got more -- and more serious traffic problems.In Grayson County along the Texas-Oklahoma border, the office of emergency management reported that bridges and overpasses were treacherous Tuesday morning. Portions of I-35 in Denton and Cooke counties also had problems.Tuesday was actually the second straight day that North Texas commuters got a taste of wintry weather. On Monday, sleet and pellets of snow fell across the region, but it was too light to cause any problems.Tuesdays high at DFW Airport was 39 degrees.