Travelers already at their vacation destinations have much to be thankful for as a Thanksgiving Day storm dumps snow and rain across the East Coast, causing travel problems for thousands still on the road.

A “mid-latitude dynamic cyclone” is producing scattered showers and thunderstorms that will spread to the East Coast on Thursday, the National Weather Service said. Parts of the interior Northeast are likely to experience moderate to heavy snowfall.

Severe storms are moving across the east coast today. Winter storm watches and warnings are in effect for parts of central New England due to the potential for heavy snow.

On Thanksgiving Eve, air and road traffic was relatively smooth until a storm in the Rocky Mountains with heavy snow caused de-icing of departing flights in Denver and Salt Lake City. According to FlightAware data, there were over 700 flight delays at Denver International Airport yesterday.

Newark Liberty International Airport, a major hub for United Airlines, experienced 95-minute delays yesterday due to a lack of air traffic controllers. That delay was lifted Thursday morning. There were over 400 delays in Newark yesterday, and 20 at 9 a.m. on Thursday.

Chris Wilbanks, the FAA’s assistant vice president for safety and technical training, told NBC News’ Tom Costello that it will take “five to seven years” for the new air traffic controllers to be fully staffed and “satisfied.”

According to FlightAware’s Misery Map, major airports Boston, Newark, Atlanta and New York’s John F. Kennedy Airports are experiencing flight delays.

Meanwhile, a record 71.1 million people are expected to travel by car for the Thanksgiving holiday, according to AAA, and that has already led to crowded streets and busy highways.

Angel Ruiz said he drove for hours to get from Tulare, California, to Los Angeles International Airport, from where he would fly to Guatemala to visit his family. He said his drive to the airport, which was normally supposed to take three hours, was longer than his flight.

“I had been traveling for maybe six hours before I got on the plane to Guatemala City,” Ruiz said. “Not a good time to travel, but I got to visit my family so I’m excited.”

Drivers should beware of rainy and sometimes snowy conditions heading to the East Coast on Thursday.

Meanwhile, lake-effect snow showers will impact the Upper Great Lakes and could bring 4 to 8 inches of snowfall over the northern shore of Michigan’s Upper Peninsula, meteorologists said.

More cold is on the way as Siberian air moving south will bring freezing temperatures – the coldest air of the season – to much of the country.