(Updates flight cancellations, emergency declaration in New Jersey)
By Carey Gillam
KANSAS CITY, Mo., Feb 4 (Reuters) - An unusually heavy winter storm slammed into the nation's mid-section Tuesday, heading east and threatening roughly two-thirds of the country with what forecasters said could be up to a foot (30 cm) of snow.
The storm system forced the closing of many state offices and schools in hardest-hit Kansas, where Governor Sam Brownback declared a state of "disaster emergency."
Authorities in Kansas and neighboring Missouri advised residents to stay in their homes and the National Weather Service (NWS) warned of extremely difficult travel conditions.
At least two people died in a car accident in Crawford County in southeast Kansas due to the treacherous conditions, state officials said. The Kansas National Guard was deploying soldiers and Humvees to transport emergency and medical workers and assist stranded motorists.
"We still have some of the most difficult conditions ahead of us as the snowfall is followed by heavy winds and bitterly cold temperatures," Brownback said. "Travel will remain treacherous and temperatures will be dangerously cold."
The conditions were so poor that part of Interstate 70, a key road artery connecting Kansas City and St. Louis, Missouri, was closed in both directions Tuesday morning near Columbia, Missouri, after several tractor-trailers collided, according to the Missouri State Highway Patrol.
"Kansas City and eastern Kansas is going to get a lot of snow," said Greg Carbin, meteorologist for the NWS Storm Prediction Center. "It's remarkable weather. Winter is entrenched. It doesn't appear to be wanting to go anywhere."
Numerous additional accidents were reported in Missouri as cars skidded off slick highways, the state patrol said.
More than 7 inches (18 cm) of snow had fallen in the Kansas City area by early evening, with more expected before the system moves northeast early Wednesday, according to the NWS.
The heavy snow and ice tracking through the central United States was headed northeast into Pennsylvania, New York and New England, forecasters said.
Areas from the lower Great Lakes eastward through central New England should see a foot or more of snow before the system moves out to sea by Wednesday night, according to the NWS, and heavy rains could result in flooding across the Tennessee Valley and Ohio Valley.
FLIGHTS DELAYED, CANCELED
More than 9,500 flights were delayed across the country on Tuesday and nearly 1,800 were canceled, according to Flightaware.com, a website that tracks air traffic.
The storm set up Monday night over southwestern Kansas and was peaking over Kansas City on Tuesday.
This event is uncommon, said NWS meteorologist Dan Hawblitzel, as only about 3 percent of the winter storms that hit Kansas City total more than 6 inches (15 cm) of snow.
Eying the approaching storm, other states were taking precautions. Connecticut Governor Dannel Malloy postponed his state of the state address by a day and said the impending storm was also causing state legislative leaders to push back by a day the start of the joint legislative session.
"While I hope the storm is not as bad as predictions suggest, I also don't want to put anyone in harm's way," Malloy said in a statement announcing the delay.
Schools in Providence, Rhode Island, were ordered closed Wednesday due to the approaching storm.
New Jersey Governor Chris Christie declared a state of emergency and ordered state offices closed on Wednesday for all non-essential workers.
"I encourage all New Jerseyans to drive carefully and remain off the roads if possible so that our first responders and public safety officials can safely respond to any emergency situations," Christie said in a written statement.
New York issued a hazardous travel advisory for Wednesday and Mayor Bill de Blasio told residents to prepare for a difficult commute.
"If you do not need to use your car, don't use your car. If you can use mass transit, please use mass transit," de Blasio said.
The snow storm comes after a fast-moving winter storm hit the U.S. Northeast on Monday, forcing flight cancellations throughout the region and tying up road traffic the day after the NFL's Super Bowl championship game in New Jersey.
On Sunday, the famed groundhog "Punxsutawney Phil" emerged from his burrow in the small Pennsylvania town, saw his shadow and - as the legend goes - predicted six more weeks of winter. (Additional reporting by Steve Barnes in Little Rock, Arkansas; Scott Malone in Boston and Dan Whitcomb in Los Angeles; Editing by G Crosse, Gunna Dickson, Cynthia Osterman and Lisa Shumaker)