18z Gfs has the 546 height line through northern Baltimore City while the Nam has it just south of DCA. IF the Nam is closer to correct with the cold air draining further south, that's enough to make a difference for some.
Gefs have not been great with snowfall this year, and downright lousy at 96+ hrs. This threat may not workout for this forum, but that remains an accurate critique of the Gefs snowfall predictions this year.
It did and consistent with the Euro's tendency for slow run-to-run changes. So I can see we'll all be running to the bathroom to check our phones at Christmas gatherings. Lol
The block is legit, but you and I have been screwed so many times over the years with 150hr+ storms and blizzards to not be surprised. It's just different IF this time it works in our favor. But, it is the Gfs, so...