Philadelphia (AP) — A plodding storm that dumped heavy snow on the densely-populated Mid-Atlantic region made roads slippery in the Northeast for Monday's commute while travel disruptions continued to ripple across the United States days after the same system first began wreaking havoc in the skies.The seemingly never-ending storm that coated parts of Texas in ice struck with unexpected force on the East Coast, blanketing some spots in a foot (300 millimeters) of snow, grinding highways to a halt and causing scattered school closures or delays. The federal government was allowing workers to arrive up to two hours later than normal or take unscheduled leave as freezing rain continued.Travel problems could linger into Monday afternoon, with freezing rain and icy conditions sticking around as wintry weather stretched across the eastern half of the US.The storm canceled more than 3 200 flights on Sunday and delayed thousands more, according to estimates from the website Flightaware.com. More than 1 300 flights Monday were already cancelled, the greatest share from Dallas/Fort Worth International Airport, which was still reeling from the effects of the ice storm that brought northern Texas to a standstill. About 650 people were stranded there Sunday night, down from Saturday night when about 2 000 travelers were stranded, spokesperson David Magana said.The forecast for Monday remained up in the air for the Northeast, depending on how quickly the system moves and temperatures rise, according to the National Weather Service. Meanwhile, a winter storm warning was issued for Washington and Baltimore, where up to a quarter inch (630 millimeter) of ice was expected because of freezing rain that could cause power outages.The expectation was for another weather system moving out of Virginia to follow the same path as Sunday's storm overnight. It was forecast to dump icy drizzle and eventually freezing rain through the New York City area and into Boston, National Weather Service meteorologist Greg Heavener said.Indeed, slippery conditions were reported overnight in the New York City area: One crash involving about 20 vehicles closed lanes of an interstate highway in Greenwich, Connecticut, for a couple of hours. No serious injuries were immediately reported.Forecasters said air travel would likely remain a hassle, too."I think the further north you look, departures and arrivals could be affected because of icy issues," Heavener said.What was forecast in the Philadelphia area to be a tame storm system with about an inch of snow gradually changing over to rain mushroomed into a full-blown snowstorm. Bands of heavy snow made for a wide range of accumulation: a foot was reported in Newark, Delaware. Philadelphia International Airport received 8.6 inches (218 millimeters), more than it had all of last year.Sunday's snow fell so heavily in Philadelphia that yard markers at the city's National Football League stadium, where the Eagles beat the Detroit Lions, were completely obscured. It was almost as bad in Pittsburgh, where the snow intensified after the opening kickoff.Heavy snow in the Philadelphia area led to a number of accidents, including a fatal crash on the Pennsylvania Turnpike that spawned fender-benders involving 50 cars, stranding some motorists for up to seven hours. More than two dozen vehicles were involved in another series of crashes on a nearby interstate highway.Stacey Jackson, a spokesperson for the Philadelphia airport, said Sunday a number of passengers were expected to remain in the airport overnight since area hotels had been full for several days. She said staff would hand out pillows and blankets to travelers to make them "feel at home even though they are not."Air passengers in the Washington-area experienced increasing delays at both Dulles International and Ronald Reagan Washington National airports.Virginia, parts of West Virginia and the metropolitan Washington area braced for blackouts under steady freezing rain, wet snow and sleet. Parts of northwest and southwest Virginia and southern West Virginia got snow, while sleet and freezing rain prevailed west and north of Richmond.But the nasty weather wasn't limited to the East Coast. In the American heartland, Nebraska and Iowa saw snow; multiple weather-related crashes were reported in Wisconsin, including two that were fatal; thousands of customers lost power in the Deep South state of Mississippi because of sleet and freezing rain.In the Southwest, a snowstorm that hit along the Utah-Arizona border left hundreds of travelers stranded on an interstate highway overnight into Sunday. The Arizona Highway Patrol said passengers in about 300 vehicles became stranded after up to 10 inches of snow and slick road conditions prompted the closure of part of the highway. There were no immediate reports of serious injuries.The specter of bad driving conditions for Monday's commute had some motorists concerned not just about getting to work but getting out at all. New Jersey's new US senator, Cory Booker, tweeted a promise to one resident to help him shovel out his car if he still needed the help in the morning.