Boxing Day Storm Chances

Apologies for not really blogging much…been a busy time here…and it’s been raining here, a lot. Up to about 6.5″ of rain since Friday and more coming tonight and tomorrow. One of the wettest December storms on record in SoCal. And 15.5′ of snow at the summit of Mammoth Mountain! Ski the West this year!

On to this weekend. The last couple weeks we’ve seen two noteworthy storm threats in the East. The first ended up going across the Midwest and burying Minnesota. The second went wide right and brought some decent snows to southeastern Massachusetts and Cape Cod (6-12″).

So this is number three. And number three is different than Nos. one and two. The players on the field are much different. But the end result is essentially the same…the East Coast and Northeast are targeted for snow and we’re about 4-5 days out. Let’s do some quick modelology and then discuss more specifics.

Morning Computer Model Forecast for Sunday Morning (from http://raleighwx.americanwx.com), clockwise from top left: GFS, GFS Ensemble Mean, Euro (Mon Morning), Canadian

The GFS has been back and forth on a storm impacting the NE. This morning’s run was substantially more suppressed with the storm, lending to very light, but widespread snow Christmas Night and Boxing Day (Sunday). The Euro has been steadfast on a fairly potent storm. And this morning’s run was absolutely epically biblical, with massive snow for a lot of folks. There’s also a Canadian model that has been flopping back and forth and today is similar to the GFS in terms of impact.

 

Right Click the image to the left and open it in a new window. These are the main model runs from this morning forecasted for Sunday morning. Let me explain. The top left is this morning’s GFS…clearly suppressed a bit and well east, but the one to the right of it is the GFS Ensemble Mean (an average of a bunch of different GFS runs with different parameterizations basically).  This looks to be slightly further suppressed and further east. That’s not uncommon, as it’s an average of about a dozen runs. But, it doesn’t inspire increased confidence.

The bottom left is the Canadian…a little more aggressive than the GFS, but still mostly a swing and a miss. But then we get the Euro at bottom right. I had to fast forward this to Monday morning, as on Sunday, it shows the center of the storm off the GA coast.  This is a massive hit for a lot of folks. Essentially 12-18″, if not 24″ over a large area.

What do I think? Here are some pros and cons…pros being things suggesting snow…cons being things that act against it.

Pros

  • Large storm system hitting much of California (this occurred a lot last year preceding the big ones in the East and has not happened yet this year.
  • European model being steadfast about a large storm.
  • NAO transitioning from strongly negative to neutral (NAO= North Atlantic Oscillation…blocking over Greenland. Often times the biggest storms are the ones that occur when this oscillation transitions from negative to positive).
  • Other factors in the Atlantic in place that would suggest a storm is possible.

Cons

  • Axis of the ridge of high pressure in the Western US is centered over Wyoming (For a major storm to hit, you oftentimes need to see this axis set up around Boise, ID. I would feel FAR more confident in this storm if that ridge axis were to set up about 200 miles further west, which could still happen, but we have a way to go).
  • Models have had a tendency to overdo storms in the East thus far this year (in terms of snow impact).
  • GFS model has not been terrible this year, and the fact that it’s showing and has trended more suppressed is not encouraging.

In a nutshell, we have things supporting this and things working against it. We need to wait until tomorrow night’s runs to REALLY get a grasp on this, as the storm hitting California will finally have come ashore. The models have done a fairly decent job modeling this massive event out West, and while that doesn’t always translate East, that means they are on to something. So if I had to break down the situation:

  • At the least, light snow is likely Saturday night and Sunday in much of the East.
  • The highest odds for significant, plowable snow is south and east of I-95, along the Jersey/Delmarva Shore and southeast New England.
  • The odds for significant, plowable snow significantly diminishes substantially north and west of the Northeast Corridor (essentially a line from Concord, NH-Danbury, CT-Norristown, PA-Frederick, MD).
  • This is a Boxing Day/post-Christmas Storm right now and Christmas Day looks satisfactory (except south of the Mason-Dixon Line, nuisance snow could snarl travel in some areas).
  • This is not a guaranteed, knock out forecast by any means.

Stay tuned on this, as there will be much to discuss in the coming days.

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