WEATHER: Will It Snow Next Week?

Posted at 5:33 PM, Mar 01, 2013
and last updated 2013-03-01 17:38:07-05

The short answer, in my humble opinion, is yes.  Medium range models continue to gradually converge on a storm track that will bring snow to the Mid-Atlantic, Virginia included, centered around Wednesday of next week.  The track, timing, and intensity can, and will to some degree, change over the next 5 days, but I’ve seen enough at this point to say we’ll see some snow.  How much snow is the biggest question, with the possibilities still ranging from a little to a whole lot.  Below is the latest Euro, bringing a monster snowfall to the Commonwealth:

Wouldn’t this be fun…or awful, if it verified?  All depends on the person.  My latest poll on my facebook page suggests 2 out of every 3 people would be elated.

state snow euro

Here’s what we have working for us:

1)  The system will move into the area quickly, but will slow down off the coast as the surface low rapidly develops into a nor’easter.  This will bring a longer period of wrap around snow into northern, central, and eastern Virginia.  The latest Euro snowfall product generates and astounding 10.3″  of snow in Richmond.  The last two somewhat aggressive runs of the Euro showed 5.9″ and 4.3″, so the 12z today is a big step up.  The GFS is now more in line with the Euro, showing 2.9″, compared to less than an inch the past two days of model runs.  These model projections are exciting, but have to be taken for what they are worth.  Will whatever falls accumulate or melt?

2)  As mentioned above, there is now much more of an agreement between the Euro, GFS, and their corresponding ensemble members.  Agreement is always a nice thing, but there have been cases where every model has been wrong…and it happens every year.

3)  The snow looks like it will be very heavy at times, increasing the probability for “loading”.  This is a process by which colder air aloft can be transferred to the surface by means of frictional drag as precip falls through the atmospheric column.  The precip essentially can pull the colder air down if it falls heavily enough, cooling the surface temperatures to a point at which accumulation will begin or become more efficient.  This loading process could overcome above-freezing surface temperatures that will likely be in place as the snow is falling.

Now, here’s what we have working against us:

1)  Even if it snows heavily, will it be cold enough at the surface to accumulate?  There are as many snowfall maps to choose from on the internet as there are opinions on the blogosphere, but many of these don’t adequately resolve the low-level cold air, or lack thereof.  There are a few possibilities for getting the air cold enough at the surface for the snow to stick.  It will either be a) cold enough at the onset of precip, which is not likely with this storm, b) able to evaporatively cool to freezing or below, which is possible given the low dew point air that should be in place c) warm to start, but cold air advection (brought in by the northerly wind) gets us to 32, or d) warm to start, but the “loading” mentioned above brings sub-freezing air to the surface.

2) As mentioned above, models have been wrong in the past and will continue to be wrong in the future.  They are also, from time to time (see the winter of 2009-2010), remarkably accurate a week to ten days or more before a system arrives.  Which result are we dealing with this go around?  It’s merely a guess, hunch, feeling, etc. at this point, and we’ve seen these systems under-perform a few times already this winter.

I’ve weighed all of the above and more in figuring out what I think will happen next week, and I do think it will snow.  How much accumulates will be the big question, but it appears as though this will be the biggest snow we’ve seen this winter, which isn’t saying much.  The graphic below indicates what I think the chances are of seeing an accumulating/measurable snow:
zach regional pops
For what it’s worth, I’m in favor of one good snow, and then onward to Spring.  I’ll continue to have updates on my facebook page leading up to the storm.  Click here and “like” my page when you get a chance and feel free to share.  Have a great weekend!  -Zach