A large winter storm that has already affected parts of the Western and Southwestern U.S. is threatening to spread south, east, and into the Northeast just in time for some of the busiest travel days of the year.

Winter Storm Boreas has already dumped up to a foot of snow in Utah and Colorado and caused 13 deaths and is now picking up speed as it heads for the Northeast. Computer models predict Boreas will bring snow and freezing rain in some parts of the interior Northeast beginning Tuesday.

Forecasters predict rain and ice will sweep across the South and converge as the system reaches 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.

Want to know how the Thanksgiving storm will affect your Turkey Day travel plans? Below is a breakdown of what Boreas will bring to each region:

Northeast

The Northeast will start to feel Boreas on Tuesday. The Appalachians, Shenandoah Valley and Upper Ohio Valley will be hit with a mix of snow, sleet and freezing rain on Tuesday morning that will spread to western, central and Upstate New York, northern and western New England by Tuesday afternoon.

The storm is expected to drop a foot of snow in Buffalo and Syracuse, N.Y., and eight inches in Pittsburgh, Kevin Roth, lead meteorologist for The Weather Channel, said.

On Wednesday, snow will accumulate from Upstate New York to the central Appalachians. Sleet and freezing rain is possible north and west of Interstate 95 from Maine to northwest Virginia. By Wednesday, precipitation should have ended, with some snow expected in northern New England and lake-effect snow.

South

Boreas is expected to bring ice to Tennessee, Kentucky, Virginia, West Virginia and parts of the Carolinas late Monday night and into Tuesday. Texas to Georgia is poised to get heavy rainfall on Monday that will spread to the Carolinas on Monday night.

The Thanksgiving storm has already hit parts of Texas, Oklahoma and Arkansas. Three people died in a dozen pileup accidents, and four were killed in Oklahoma, officials told NBC News.

The Dallas-Ft. Worth Metroplex has a winter weather advisory is in effect. American Airlines has canceled more than 300 flights today, roughly one-third of its scheduled departures.

The National Weather Service has issued a storm warning for North Texas until midday Monday, and Oklahoma is under a winter storm warning, as well as southwestern Arkansas.

When will the storm end?

By Thanksgiving Day, the storm will have tapered off. The Northeast will still get some snow, but the rest of the country should experienced a calm but cold Turkey Day.

New York Winter Thanksgiving Storm