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.