Heavy snow for parts of the Northeast at midweek
1. A storm crossing the Plains will weaken, but a second storm is likely to form in the Carolinas late Tuesday and affect the Northeast on Wednesday. This is the GFS ensemble snowfall prediction through 1 a.m. ET Thursday

This suggests a sharp gradient between little or no snow at or just offshore to heavy snow a little more inland. In the heaviest snow area, there could be tree limb and electric line damage, as well as poor travel conditions.
2. Meanwhile, it will be dry and chilly across most of the Great Lakes and Northeast today. This map shows the pressure pattern as of 7 a.m. ET

3. The storm should have little impact in the Northeast until after Tuesday evening. This map is for 7 p.m. Tuesday:

There can be a large area of mostly light snow showers from the Great Lakes into the Appalachians at this time. However, the size of the gray area is often related to differences between individual members of the ensemble. If one member shows snow in Iowa and a second shows it in Ohio, the averaging process puts snow in both places on the ensemble mean map.
4. On Wednesday evening, the storm is likely to be at its peak in the Northeast corridor:

5. Cold dry air will follow the storm later in the week.
Today's video (blog version)
Elliot Abrams' Video Blog
