Signs are pointing toward a shift of the polar vortex that may be accompanied by a significant storm with rain, snow and wind in the northeastern United States during the days prior to Thanksgiving.

The polar vortex is actually a storm in the upper part of the atmosphere that typically hangs out within the Arctic Circle. Arctic air is usually locked up within the bounds of this storm.

Occasionally, the polar vortex is dislodged, stretched or split into multiple parts. When this happens, arctic air can push southward to the mid-latitude regions anywhere around the globe.

"A southward stretch of the polar vortex is possible around the days prior to Thanksgiving (Nov. 18-22)," according to AccuWeather Lead Long-Range Meteorologist Paul Pastelok. "A piece of the vortex may break off and settle toward the Great Lakes."

When cold air drops southward across the Midwest and into the East, a major storm can be spawned.

The area along the Atlantic Seaboard is often a perfect breeding ground for storms in situations like this, according to AccuWeather Meteorologist Evan Duffey.

"The clash between the arriving arctic air and the warm waters of the Atlantic Ocean could help instigate a major storm several days before Thanksgiving," Duffey said.

This spin-off storm can pose major travel problems if cold air is captured fast enough to produce heavy snow inland and heavy rain and wind on the coast. Beginning next weekend, travel typically ramps up as some people begin to head to Thanksgiving destinations.

The magnitude and path of the cold air as well as the exact formation and track of the spin-off storm may become clear later next week.

Based on climatology, accumulating snow is much more likely to fall over the higher elevations from north and west of Interstate 95 to the Appalachians into the first part of winter. This is due to the impact of the relatively warm Atlantic Ocean.

"There is the risk for the first major snowfall somewhere in the Northeast during the period from Saturday, Nov. 18, to [Wednesday,] Nov. 22," Pastelok said.

In this case, the risk may extend to part of the Atlantic coast.

If the spin-off storm forms farther west, over the Great Lakes area, then warmth with rain on the Atlantic coast will simply be followed by a cold blast with dry air.

For parts of the Midwest and the Northeast, the arctic blast may bring cold air farther south than the event this weekend.

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As if the storm and arctic blast were not enough, a second stretch and breaking of the polar vortex may occur close to the Thanksgiving weekend. Yet another storm may arise as that new round of cold air takes root.

While the weather pattern may end up being less volatile than these scenarios suggest, people with Thanksgiving travel plans should continue to monitor the forecast over the next week.

Regardless of the storm potential, people planning on traveling by car through the Thanksgiving weekend in the Northeast and Midwest should make sure their vehicle is prepared for winter travel conditions. A set of tires with decent tread, new wiper blades and adequate fluids are a good start in advance of the trip.

At the very least, the polar vortex will help send more cold air, periodic snow, wintry mix and/or lake-effect snow squalls from the Upper Midwest to the interior Northeast in the days leading up to and following Thanksgiving.

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