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Snow this morning, snow tomorrow night

Fredericksburg finally broke the snow jinx for this winter thanks to the Alberta clipper that dropped a couple of inches of white stuff over the area.  The total depth was a bit more than the one inch or so that I’d expected given (a) the clipper chose the ‘Burg as the bullseye for a single heavy band of snow and (b) the very cold temperatures (overnight low at the UMW weather station was 14 degrees (F)).  The normal snow:water ratio is 10:1, i.e. ten inches of snow for one inch of available liquid, but when the current Arctic temperatures got involved this ratio doubled to around 20:1 producing a very fluffy snow.  If this had been a more typical Fredericksburg snowfall with temperatures closer to the freezing mark we would have seen about half of the amounts that the area actually received.

Another effect of the very cold temperatures is that everything that fell stuck and the “slipperiness factor” became significant in a hurry.  The roads quickly became difficult to drive on and sidewalks became hard to walk on so be careful out there today.  This won’t improve much given today’s forecast high temperature in the upper 20′s and a low tonight in the teens.  Then the next clipper pays us a visit.

Here is the forecast surface map for Friday evening:

As I mentioned in yesterday’s post there would be two systems involved, one being another Alberta clipper (the red L near the Great Lakes) and the other a southern system (the red L over northern Georgia).  These two systems will “phase” – join forces – off the East Coast but not early enough so we would see a substantial snowfall Friday night into Saturday.  As it stands now the models show this strengthening just beginning to occur as this complex system passes through the Mid-Atlantic, providing the possibility that another heavy band of snow or two could form and concentrate snowfall totals in a small area.  Forecasting where such a band might occur at this point would be a lot like trying to predict where a summertime thunderstorm complex will form and what neighborhoods it will affect.

Thus a reasonable conclusion to draw right now would be that the ‘Burg will receive another 2-3 inches of snow from this system, and that’s pretty much what the National Weather Service forecast graphics indicate.  (Of course a heavy snow band that targets the ‘Burg again could up those totals in a hurry.)  The precipitation will start mid-afternoon Friday and continue for 6-8 hours as this fast-moving system zooms through the region.  That, unfortunately, means the normally busy Friday afternoon rush hour could be a tangled mess so you may want to plan ahead for a longer drive home.  More on this system and the weekend outlook in tomorrow’s post.

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Permalink: http://news.fredericksburg.com/weather/2013/01/24/snow-this-morning-snow-tomorrow-night/