Round 2

For a few days now, both the GFS and the NAM (which is a good short-term model) have been suggesting a reinforcing shot of cold air would come through our region overnight and into the day tomorrow along with enhanced upper level dynamics.  This combination was indicative of a second burst of snow that would begin early tomorrow morning and continue into the afternoon.

It now looks more likely that this will happen.

The only thing that gives pause is the Euro model which has insisted for a while now that any precipitation will be pushed south of our region.

The primary difficulty in this forecast is less what type of precipitation will fall (as it was in the last storm) but how much.  A lot of the snow totals could largely depend on small localized banding events.  If one of those bands forms overhead, it could mean the difference between 1-3 inches and 3-6 inches of snow.

One thing we have going for us is the push of cold air aloft which should mean enhanced liquid-to-snow ratios. 

Here's the GFS snow total map for this storm:

you can see the bullseye in the Baltimore area but we in the DC metro are still doing pretty well - in the 3-6 inch range, generally.  When I look at the projected temperatures at the 850 mb level:

I see a lot of -4 and -5 degree readings overhead which suggest to me a liquid-to-snow ratio a little higher than the standard 10:1.  Maybe as much as 15:1.  This means that whatever falls will accumulate and quickly.

The DC metro is under a Winter Storm Watch for tomorrow morning for 3-5+ inches of snow.  I think this is reasonable based on the GFS and NAM model forecast.  I'm going to wait to see the Euro before I get too excited but, in summary, prepare for more snow starting early tomorrow morning and accumulating quickly.