What makes tracking this system - a system that's more than 1,500 miles wide - so difficult is that the New York metropolitan area, with its 20 million-plus people, is at the northern edge of the front.
Now, as Lee points out, every system has a northern front. But this time, we happen to be on the edge of it - something that doesn't happen very often.
Which is why Lee says that there's a 50-mile Twilight Zone kind of area where some New Yorkers on the southern edge could get a foot of snow while those on the northern edge could get an inch.
It's a wild variable.
Lee's tracking it all for us - and he leads our coverage tonight at 11. We also have reporters out in it, especially in New Jersey, which will get the worst of it in the tri-state.
Also at 11, two murders involving children - and they're just horrible stories.
The first involves an 8-year-old boy found dead in the Peninsula Hotel in midtown Manhattan. A woman was also found in the room, in critical condition. Police say it's the boy's mother and have identified her as Gigi Jordan. Cops say she was distraught over the demise of her marriage - so, they say, she killed her son and then tried to kill herself.
The other murder involves a 3-year-old boy and his mother, whose bodies were found in the woods in Hauppauge on Long Island. So far, there are no suspects and no motives. But it is a strange and disturbing case.
We'll also have any breaking news of the night, plus Scott Clark with the night's sports.
I hope you can join Liz Cho and me, tonight at 11, after 20/20.