Hereford Zone: 2-4 inches
Immediate Baltimore metro area: 1-2 inches
DC, Northern VA, Annapolis: coating
Southern MD: nothing

Discussion:
All models are on board for rain changing to snow for Baltimore as a low passes by to our south then strengthens. The timing of rain changing to snow should be a couple hours before dawn Thursday morning. Snow should be over by mid-day (except see below). A number of model runs have placed 4-6 inches in the downtown Baltimore area. I seriously doubt this will be the case and antecedent warm conditions will largely prevent the roads from becoming too bad (pavement temperatures are currently in the 50s) and snow will likely only accumulate on grassy areas and cars. In fact, the farthest south the actual freezing line gets in any model run has been Baltimore. The Hereford Zone and other areas of Maryland near the Mason Dixon line may receive 6 inches if the air gets cold enough fast enough. As for schools, snow should be falling at dawn with a forecast of snow through the morning, so come to your own conclusions based on that information.

A big boom scenario would put 6 inches in downtown Baltimore and 3 in the DC area, but I find that very unlikely to occur and would be dependent on the low pressure hanging on the coast for a bit before ejecting east-northeast. The bust scenario is the more likely one to occur between boom/bust and that would be an all rain event, even for Baltimore, with perhaps a coating of snow at the end.

An upper level trough will swing through behind the low pressure system later Thursday around the evening rush hour. This could result in snow squalls that could produce a half inch of snow in any given location and this applies to the whole area including DC and southern Maryland.

Regarding the snow chances later Wednesday night or Thursday, models are saying a small area of low pressure is going to form towards southwest VA or western North Carolina and track east-northeast from there. This is after the cold front has passed by, which would indicate a rain changing to snow scenario. There are several reasons to believe there won’t be that much snow or if snow falls, it won’t have much impact:

1. It will be very warm tomorrow and Wednesday.
2. Snow chances are entirely dependent on low track.
3. This low would be weak sauce.
4. Models have only brought the snow line down to Baltimore in their runs that have snow, while many runs have had it stay north of the Mason-Dixon line.

However, the euro has been tracking the low just right so it will be curious to see what happens. The GFS has also developed a second small band of snow Thursday afternoon or evening. I wouldn’t be surprised if enough snow falls to mess up the Hereford Zone at some point. As for the rest of Baltimore County, I have my doubts that there will be anything of significance to cause a delay or closure. DC, northern VA and southern MD look shut out from any real snow possibilities from this one.

The 18z GFS produces 3.5 inches for Baltimore City through Thursday evening assuming a 10:1 ratio. It’s highly unlikely that all of this would stick, even if 3.5 inches worth of snow were to fall.

 

The Kuchera method of measuring snowfall from the model produces 1.5 inches and this is a more realistic result for this run.