Time to Start Thinking About the Milk and Toilet Paper...

The Washington Post's Capital Weather Gang has the following analysis:

Here is the current (VERY EARLY) probabilities on accumulations:

40% chance: Less than 1"
20% chance: 1-4"
20% chance: 4-8"
20% chance: 8"+

I recommend you skip the caveats, as well as the fact that less than 4" is the most likely scenario to focus on the fact that 4-8" isn't even the worst case.