Mother Nature to deliver arctic blast for Christmas

Dec. 20 (UPI) -- The next major winter weathermaker will take shape just in time for Christmas this coming week, threatening to snarl travel and bring bitterly cold air. However, for some dreaming of a White Christmas, it will come just in time.

"A large dip in the jet stream in the East this coming week will lead to mayhem and mischief just in time for the holiday," AccuWeather Broadcaster and Senior Meteorologist Bernie Rayno said.

A potent storm system will take shape Tuesday as it slides eastward across the Rockies, the last storm in a train that has relentlessly slammed the Pacific Northwest.

As it emerges in the Plains during the middle of the week, an Arctic blast of cold will surge south and then east through the end of the week. The blast of cold air will also contribute to snow right before Christmas for some. Wind and rain will also pick up, leading to a full bag of weather hazards that will accompany this storm.

"Where snow begins to form in the Plains for the middle of the week will depend on exactly where the center of the storm takes shape," explained AccuWeather Senior Meteorologist Tyler Roys.

"The leading edge of this Arctic blast will be the boundary along which the main center of low pressure forms, but confidence is still low on just where that center will form."

Forecasters say the rain could be heavy enough to cause some flooding concerns, especially when combined with melting snow in the Northeast. Strong winds and severe thunderstorms could also become a threat with this storm.

However, cold air quickly sweeping in behind the storm will also cause a large area to see a change to snow again before the storm ends. In the Great Lakes, the cold air will crank up the lake-effect snow machine in the wake of the storm. Depending on the exact evolution of this storm, a change from rain to snow could even occur well into the Southeast.

The snow could persist long enough to bring a fresh, white blanket just in time for the holiday, but also slippery, snow-coated roads as well.

Even for locales that don't see a change to snow, or don't see any accumulating snow before the storm ends, another threat will lurk in the wake of the storm.

"Behind this storm a blast of truly bitter cold and strong winds is going to surge all the way to the Gulf Coast," Roys said.

Temperatures will plummet in the wake of rain and snow and can lead to a rapid freeze-up across a vast stretch of the eastern U.S.

Places like St. Louis or Little Rock, Ark., could see rain with temperatures in the 50s Wednesday afternoon, then quickly see temperatures crash into the 20s Wednesday night. Untreated surfaces still wet from afternoon rain would quickly turn into a sheet of ice.

Areas farther east would suffer the same fate on Christmas Eve. Buffalo, N.Y., and Pittsburgh could be in the 40s with rain Christmas Eve day, before temperatures crash into the teens with rain changing to snow for Christmas Eve itself.

Even the Gulf Coast coast will not escape the Christmas chill as even cities along the coast such as New Orleans; Mobile, Ala. and Pensacola, Fla., could wake up to temperatures in the 30s Christmas morning. Widespread frosts and freezes are likely all across the Deep South.

Yet rain, snow and cold are still not the only facets this storm will offer. Driving winds will also accompany the system.

"Strong winds will develop both ahead of and behind the storm," Roys said. "The greatest chance for winds to be locally damaging will be Wednesday in the Central Plains, and then potentially Christmas Eve or Christmas Day along and near portions of the mid-Atlantic and New England coast."

Even where winds on the backside of the storm aren't strong enough to cause much damage, they will still combine with the Arctic air to produce dangerous cold.

When combined with the already well below-normal temperatures, AccuWeather RealFeel® Temperatures could plummet well below zero Christmas Eve and Christmas Day all the way from the Northern Plains through the Great Lakes, Ohio Valley and central and southern Appalachians. At these temperatures, frostbite can set in on exposed skin in just a few minutes.

While the core of the cold will ease towards the end of the holiday weekend into the following week, forecasters say that colder weather will persist into the new year.