Already, there are dozens of flooding reports across the South in the last 48 hours from Louisiana to West Virginia, where more than a half a foot of rain fell. Some homes are completely surrounded by water in Alabama.
On the cold side of this storm system, in New Mexico more than a foot of snow has already been reported, and up to 3 inches of snow is reported in western Texas.
This morning, 36 states from the Rockies to New England are under snow and flood alert, including a blizzard warning for three states in the Northern Plains.
As the storm moves east, severe thunderstorms are expected to break out in the South from Mississippi to Alabama and Tennessee, where the biggest threat will be damaging winds up to 70 mph and a few tornadoes.
Also, flood watches have been issued from Texas to Pennsylvania, where heavy rain could cause significant flooding.
On the northern side of this storm system, snow is expected to break out from Oklahoma to the southern Great Lakes, where a winter weather advisory has been issued. Some areas could see up to a half a foot of snow.
By Wednesday night and into Thursday morning, this storm system will head east and will bring rain and snow to the Northeast where a winter weather advisory has been issued from Pennsylvania to Maine. Some areas away from the coast could see up to half a foot of snow.
Major cities such as Washington, D.C., Philadelphia, New York City and Boston will see mostly rain, but as the storm moves in Wednesday night, some precipitation around New York City and Boston could start as snow and then quickly change to rain.
Heavy rain is expected Thursday morning from New York City to Boston.
In the Carolinas, this storm system could bring strong to severe storms, with damaging winds being the primary threat.
Behind this storm system, most of the eastern U.S. will get hit with a blast of Arctic air, which has been rare this mild winter season.
Wind chill advisories have been issued for the Midwest, where it could feel as low as -45 degrees.
The cold air arrives into the Northeast by Friday, with temperatures crashing -- and with the wind, wind chills will be below zero in New England and single digits from New York City to Boston.
This will be a major shock to the senses since temperatures been very mild so far this winter.