(NBC) - A deadly winter storm system is threatening plans for millions of Americans who will fly or drive somewhere for Thanksgiving — with some of the worst weather expected on Wednesday, the busiest travel day of the year.
Storms have already heaped up to a foot of snow on the mountains of Utah and Colorado and claimed 13 lives, including a 4-year-old girl who was killed in a rollover crash on an icy road in New Mexico.
Now the weather pattern is picking up speed and heading for the Northeast, and the 43 million Americans who plan to travel for Thanksgiving are at risk. Rain and ice sweeping across the South will converge with a storm system pushing down from the Great Lakes.
“That is a lethal combination for winter weather in the Northeast,” said Tom Niziol, a winter weather expert for The Weather Channel.
Among the 43 million travelers are 3.1 million expected to fly. Flights could be delayed in New York, Boston, Washington and Baltimore. That is because of expected low clouds and strong wind, said Kevin Roth, lead meteorologist for The Weather Channel.
In the Northeast, the worst weather is expected Tuesday and Wednesday.
“If people traveling can get out before then, or wait until afterward, that would be the best thing,” Roth said.
The system moving across the South is expected to bring ice to Tennessee, Kentucky, Virginia, West Virginia and parts of the Carolinas late Monday night and into Tuesday.
On Tuesday, it will link up with the system pushing down from the Great Lakes, bringing heavy snow to parts of Pennsylvania and upstate New York, and heavy rain closer to the Northeast coast.
The storm is forecast to dump up to a foot of snow on Buffalo and Syracuse, N.Y., and up to eight inches on Pittsburgh, Roth said.
After a frigid, blustery weekend in the Northeast, 1,000 people were already without power in Connecticut after high wind brought down a power line, NBC Connecticut reported.
The storm system threatening Thanksgiving plans started in the West on Thursday, where it killed three people in California. It moved on to New Mexico and Texas, both of which were under winter storm warnings Monday.
Up to 11,000 people were without power in parts of Texas over the weekend, the utilities said, and NBC Dallas Fort-Worth reported that 300 flights were canceled there Saturday and Sunday in anticipation of ice.
The storm sped up and moved on through Texas, Oklahoma and Arkansas. Three of the people died in a pileup of a dozen vehicles in the Texas Panhandle, and four were killed in Oklahoma, officials told NBC News. Another man was killed in flooding in Arizona.
By Thanksgiving Day, the system will have moved out over the Atlantic Ocean.
By Alexander Smith and Erin McClam, NBC News