There are two different low pressure systems to deal with in the Mid-Atlantic region between now and Friday night. The first system is dropping southeastward from the Great Lakes region and it can generate snow showers in the Mid-Atlantic pretty much anytime from this afternoon into early Thursday morning. The greatest impact from this clipper system will be late tonight and early tomorrow across northern Virginia, northern Maryland and DC where an inch or two of snow could fall, but even the Philly and NYC metro regions can see some snow shower activity from this afternoon into early tomorrow with a quick coating possible. Any snow that does fall can quickly create slick road conditions given the bitter cold temperatures; especially, where heavier snow bands set up towards morning, for example, in and around the DC metro region.
The next system in store for the Mid-Atlantic looks to me like it’ll produce a light-to-moderate snowfall during Friday afternoon and evening despite the fact that some computer forecast models are trying to write it off (e.g. NAM). The crucial upper-level energy associated with this still developing system is just now coming ashore from the eastern Pacific Ocean and I believe the computer forecast models are just now getting a better handle of things. In fact, the very latest GFS and Canadian model runs have increased their precipitation amounts slightly for Friday afternoon and evening and we’ll see if that begins a new trend. Accumulations estimates for Friday afternoon and evening continue to be in the 1-3 inch range with isolated 4 inch amounts possible – stay tuned on that. Meanwhile, the bitter cold temperatures continue and will do so right through Sunday.