Northeastern US temperatures to plunge and rise dramatically into the new year

The weather pattern will feature big temperature swings over the northeastern United States into the first week of the new year.

In the span of less than a week, from Thursday, Dec. 29, to Tuesday, Jan. 3, AccuWeather RealFeel® Temperatures may plunge and rise by as much as 50 degrees Fahrenheit.

Some people will be reaching for midwinter coats one day, then seeking lightweight outerwear the next.

"The jet stream will plunge southward and pull northward a couple of times over the next week to 10 days," according to AccuWeather Long-Range Meteorologist Mike Doll.

The jet stream is a fast river of air located at a height above the ground where jets cruise at. The jet stream guides weather systems along and often separate cold air to the north from warm air to the south.

Mild air that lingered across the region early this week will slip away later this week.

"The air will turn sharply colder late this week in the wake of a big New England snowstorm," Doll said.

Expect the cold spell to unleash bands of snow downwind of the Great Lakes. Snow flurries can reach as far as the mid-Atlantic coast on Friday.

When compared to the peak of the warmth this past Tuesday, actual temperatures will be about 20 degrees lower by Friday and Saturday.

Temperatures will dip to a few degrees below average for the last two days of December. High temperatures are projected to range from the upper teens and lower 20s in northern Maine to the middle 40s in southeastern Virginia.

Temperatures at night to end this week will dip 10 to 20 degrees lower.

RealFeel Temperatures will dip to near zero in the upper part of the Northeast and to the single digits and teens at times as the week draws to a close and the weekend begins.

However, the cold air will not be able to take root and is likely to sound the retreat as the New Year holiday weekend progresses.

The warmup will commence following a weak storm system with snow showers that sweeps through from Saturday to Sunday.

"That weak storm will not have enough time to pull much cold air southward from Canada," Doll said.

New Year's Eve Times Square revelers can expect about average conditions. Temperatures are projected to be in the upper 30s with the chance of a rain or snow shower.

Temperatures on New Year's Day will climb through the 40s in Philadelphia for the Mummers Parade.

"Another big storm over the Central states will pull milder air into the Northeast for the start of 2017," Doll said.

Temperatures are likely to turn around quickly enough to prevent the storm from bringing heavy snow to most of the region from late Sunday to Tuesday. However, at the onset of the storm, temperatures near the ground may be cold enough in parts of the central Appalachians for a brief period of ice.

As many people head back to work or school during the middle days of next week, temperatures are likely to average above normal.

Highs next Tuesday will range from near 30 in northern New England to the middle 60s in southeastern Virginia.

Another surge of cold air and lake-effect snow are likely to follow prior to the end of next week.

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