April 9 (Reuters) - A spring snowstorm hit Colorado on Tuesday, cancelling flights and closing schools as forecasters warned the middle of the United States to brace for sleet, gusty winds, flash flooding and tornadoes.
"A dynamic storm system evolving over the central United States will impact much of the nation with a variety of hazards," the National Weather Service said.
Rain turned to snow overnight in the Denver area, which was forecast to get up to 11 inches (28 cm) of snow, and temperatures dipped into the teens.
Airline tracker FlightAware.com said 175 flights in and out of Denver International Airport had been cancelled. Most schools in the Denver area were closed, the Denver Post said.
Moderate to heavy snow and gusty winds were forecast for Colorado, Nebraska, South Dakota and Wyoming.
Areas south and east of the snow will see sleet and freezing rain and potentially flash flooding as the storm moves east, the Weather Service said.
The arctic air sweeping east will mix with warm, moist air surging north from the Gulf of Mexico, bringing heavy downpours, damaging winds, large hail and possibly tornadoes to the central part of the nation.
The tornado season in the United States typically starts in the Gulf Coast states in the late winter, and then moves north with the warming weather, peaking around May and trailing off by July. (Reporting by Jane Sutton in Miami; Editing by Eric Beech)