Tuesday, February 14, 2012

Potential For Weekend Storm System

It wouldn't be President's Day without at least some computer modeling hinting...and suggesting...the potential of a storm system along the East Coast at some point over the upcoming three day weekend.  There is a pretty wide spread in modeling at this point regarding the upcoming weekend...

First, the model that shows the potential for a storm system.  Last night's run of the Euro is suggesting that this system tracks just off the East Coast and throws snows into the Mid Atlantic, north to the south coast of New England...with the best wintry precipitation falling across Virginia, Maryland, and into New Jersey.  Temperature profiles suggest this system may be a rain to snow scenario for coastal sections, with a better chance of snows farther inland as there isn't a huge supply of cold air available with the storm system as the Euro depicts it.  If it's strong enough, dynamics might be able to thump enough cold out of the upper atmosphere to yield a bit more snow...  However, don't get excited.

The GFS from the same timeframe (last night) and forecast for the same time (1 PM Sunday) has the center of low pressure east of Savannah, as opposed to east of Norfolk.  The GFS has generally supported a solution that keeps the storm tracking far enough to our south to miss the region altogether.  You can see the several hundred spread between the two camps as the GFS is suppressed, while the Euro brings the storm up the coast.

Why the difference?   The mid level chart below should shed some details on this.  First, the GFS has a more pronounced trough over New England and Eastern Canada than the Euro, which has a much weaker mid level low over the same region.  Notice the blue shading over the Gulf of St. Lawrence on the GFS whereas the EC is merely light green.  The deeper and stronger trough over the Northeast acts as a road block on the GFS to prevent the storm system from lifting north.   On the European model, the trough is displaced a bit to over the Great Lakes with a ridge of high pressure (oranges) over the Western Atlantic.  This allows the storm to ride up the East Coast somewhat as the mid level low over Newfoundland is much, much weaker in comparison.

If the Euro solution were to verify, this storm would not necessarily be all snow as depicted.  Temperatures at the surface and in the lower atmosphere are marginal at the front end of the storm so there would probably be some rain...especially along the coast and inland through Delaware and South Jersey.  That rain could probably end as a period of snow but it's not a clear cut "gonna snow" solution since there isn't a strong fetch of Canadian chill feeding into the storm.  Not to borrow a "cliche phrase" but the storm would need to be rather dynamic and self-generate or draw down cold air from aloft to compensate for the relative lack of cold in place.

There's lots of time ahead of us to watch...and thankfully, neither solution is "locked" at this point as much can change.