The heaviest snow is expected to fall between 11 a.m. and 2 p.m. before tapering off during the mid-afternoon hours, NY NJ PA Weather's Steven DiMartino advises in his latest video forecast issued around 9 a.m. today.

During that period, heavy snow will fall "from Long Island, just to the south of NYC, and back to the Philly metro area," according to DiMartino. 

[10:30 A.M. UPDATE IS HERE.]

There will be bands of intense snowfall, delivering the chance of "thundersnow," a term made famous in this video of The Weather Channel's Jim Cantore

DiMartino explains in his video: "You have a highly unstable atmosphere, much colder temperatures aloft. That leads to rapidly rising air, very heavy snowfall as a result, and so you end up what what's called convective snowfall."

He says that connective snowfall "leads to more electrons in the atmosphere, which leads to lightning and the potential for thundersnow."

Before all is said and done, much of the area will likely see three to six inches of snow, with potentially more than six inches where the heaviest bands form.