A series of storms moving across the country will bring significant snow and ice to the north and heavy rains to the south Friday and into the weekend.
Roughly 100 million people are under some form of a winter storm watch, warning or advisory across the United States.
The storm is already affecting travel with nearly 450 flights canceled as of Friday morning, according to FlightAware.com. Airlines are issuing waivers for travelers traveling in the Midwest and Northeast.
Major metro areas on the East Coast likely will face light snow Friday ahead of and during the morning commute. The storm should move so quickly that accumulations are expected to remain low in New York and Boston.
The second storm is associated with the same upper-level energy as the West Coast storm that has dumped inches of rain in cities such as Los Angeles and caused blizzard conditions in the Sierra Nevada.
Snow is likely in places like Kansas City, St. Louis and Chicago
The second storm exits the Rockies and will begin to drop snow late Friday across Kansas.
In Missouri, Kansas City and St. Louis -- which received the brunt of last week's storm -- will see less accumulation with this system. However, winds could gust up to 35 mph, causing blowing and drifting snow through Saturday night.
Lake effect snow will help enhance the amounts that Milwaukee and Chicago could see through the weekend. Both could see over half a foot of snow if the conditions remain right.
Indiana and Ohio could see rain to the south, inches of snow to the north and ice and snow across the central portions of the states.
Significant icing event is possible along I-95 corridor through New England
The second storm will be more significant for the Northeast than the first.
As the low tracks farther east, warm air is likely to mix in from the South. At this time, it's uncertain exactly where the line between rain and snow will form.
Forecasters expect a substantial amount of precipitation Saturday evening through Sunday up and down the East Coast. It's unclear on the timing of what type of precipitation is expected for metro areas in the Northeast.
This situation is reminiscent of an event earlier in the season when forecast models were showing warmer air leading to little or no snow totals. The models all came true, except in New York, where the colder air spilled in and inches of snow caught many New Yorkers by surprise.
CNN Meteorologist Chad Myers said the storm in November was more difficult to forecast because it was early in the season when the models are just beginning to run winter equations, and the actual air profile doesn't act like winter yet.
"Now that we are in the middle of winter the models should do better with this storm."
The latest model forecast indicates places such as Boston and New York will see snow starting Saturday evening, which will then turn into more of a wintry mix and freezing rain overnight into Sunday. New York is likely to warm up enough to see rain Sunday morning. But even if some precipitation doesn't freeze on contact Sunday, it will freeze by Sunday evening when the temperatures plummet.
Similar to the November storm, there is a steep gradient between rain, ice and snow. Meaning close to the coast people could see rain, a few miles inland freezing rain mix, a few more miles inland snow mix and then a few more miles away the snow starts piling up quickly.
Winter storm watches are already posted for upstate and inland New England. Heavy snow and sleet will pile up 6 to 12 inches deep (likely more) with some icing for added misery.
The I-95 corridor through New England seems to be where the bulk of the ice will set up, with up to an inch of freezing rain possible in Connecticut, Rhode Island and Massachusetts.
A flash freeze is likely behind the storm
Behind this second storm, a deep chill will grip much of the eastern half of the United States.
It may warm up enough to see rain across the Midwest and Northeast on Sunday but will quickly dip below freezing. That could happen so fast it would instantly freeze any remaining moisture on the ground or surrounding objects.
Highs on Sunday in the Kansas City area -- where the Chiefs will host the New England Patriots in the AFC Championship game -- will be in the 20s.
The extreme cold follows the storm and moves into the rest of the Eastern United States on Monday.
The National Weather Service in Boston said it's expecting "a roller coaster of temperatures through this portion of the forecast" and "a prolonged period of well below normal temperatures early next week."
Keep the hand warmers handy, because temperatures won't just be below average Sunday and Monday.
"For the most part, this winter the jet stream has traveled horizontally across the US. Sure, there have been some ups and downs, but nothing like what is to come," CNN's Myers said.
"By next week the jet stream will flow from Fairbanks (Alaska) to Texas. So, for example, the following Saturday Anchorage will be 32 and Chicago will be 13."
This arctic air will spill out across the country later next week as far south as Florida, leaving most of the continental United States with below-average temperatures.