(CNN)Monday marks the beginning of "astronomical winter" and the Christmas week forecast calls for plenty of possibilities for snow, at least for some.
Known also as winter solstice, astronomical winter begins December 21 -- with weather prediction models showing a growing potential for a strong winter storm. The storm will sweep from the Midwest to the East later this week bringing with it snow and heavy rain.
The system carries the potential for severe weather Wednesday through Friday. And cold air pushing in behind it means even southern states could end up seeing snow flurries at the end of the week.
Multiple systems with rain and snow
A storm system Monday is expected to bring a round of light snow to the Great Lakes region and into the Northeast, just days after a historic Nor'easter pummeled states including Pennsylvania and New York with over three feet of snow.
Snow is also in the forecast for higher elevations in the western US. The Cascades could see 1 to 2 feet of snow while the Rockies and Tetons could see 6 to 12 inches of snow through Tuesday.
A stream of Pacific moisture continues to inundate the Washington and Oregon coasts with heavy rain that is raising flood concerns. Rivers, creeks and streams are expected to swell, and burn scar areas from previous wildfires will be especially prone to flooding this week.
The western system will intensify as it moves eastward across the country Tuesday and Wednesday, which in turn could produce very heavy rainfall and potentially severe weather to the eastern half of the country later in the week.
Currently, models are showing snow across the central Plains and Midwest on Wednesday, with rain from the Great Lakes down to the Gulf Coast.
"By Thursday this system could bring snow to the Great Lakes and heavy rain to much of the East Coast," said CNN meteorologist Haley Brink.
By Christmas Day, the Northeast and Mid-Atlantic could see some snow. Some models indicate that snow flurries could fly overnight Thursday into Friday morning as far south as Atlanta.
Rain will be the main focus for Boston as we finish out the week, which will likely melt any remaining snow on the ground. It's also going to be warm with high temperatures in the low 50s, which means that Christmas in Boston will likely be warmer than Halloween was in Boston when they only hit a high of 42 degrees.
Boston isn't the only city that will be dealing with abnormal temperatures this week,
St. Louis will feel like it's having two different seasons this week, going from a high in the mid 50s Monday down to a high only in the upper 20s by Thursday.
Denver is forecast to have a high of near 60 degrees Tuesday, then quickly drop to a high of only around 30 the next day.
The start of the week will be balmy for the central portion of the country, when temperatures will range from 15 to 25 degrees above average from North Dakota down through Texas. As that warmth spreads east on Wednesday and Thursday, it will be replaced by much colder air. By Thursday temperatures will average 10 to 15 degrees below normal from Minnesota to Mississippi.
By Christmas Day, Indianapolis, Cleveland, and Washington, DC, will have high temperatures about 15 degrees below normal.
Even South Florida will see cooler temperatures. Miami, Tampa, and Orlando will all have high temperatures averaging about 10 degrees below normal on Christmas Day.
Temperatures out West, particularly around the Four Corners region, will be above normal to start the week, but will see a cool down by Wednesday.
The US Centers for Disease Control and Prevention does not recommend traveling this holiday season, saying it is safer to celebrate at home.
Three-quarters of Americans are expected to do just that this holiday season, according to AAA.
But the other 85 million who might travel from December 23 through January 3 should keep an eye on the weather, as several systems will be moving across the country.
Atlanta Hartsfield-Jackson International Airport expects less than half as many holiday travelers as last year, officials said.
December 27 is projected to be the busiest travel day at the world's busiest airport. More than 2.1 million passengers will travel through it between December 17 and January 3.
The question is, will Mother Nature cooperate?