Saturday, December 29, 2012

A Not-So-Smooth Transfer Of Energy

It's a bit of a misnomer to say today's outcome is that of a warmer storm. It certainly isn't all that warm outside this morning and the atmosphere is cold enough to generally support snow for most locations in Philly and points northwest if there was sufficient moisture...although it would be a wet snow. However, the problem is that we're dealing with two separate pieces of energy that are remaining distinctly separate and look to provide a 7-10 split on precipitation over the Delaware Valley.

Northern energy continues to hold firm and isn't giving up quite as quickly as we thought...between this and the developing coastal off of the Carolina coastline, usually you see a precipitation or energy transfer take place as the coastal feature intensifies and becomes the dominant feature. The timing on this transfer is always the tricky part and for the most part modeling was suggesting that transfer would take place near the Delaware Valley.  However, the northern feature is maintaining itself longer...and thus that separation between it and the coastal will hold firm into our region as well.

This really shows up in the precipitation breakdown on the GFS from earlier this morning -- the northern feature spreads a healthier swath of precipitation to our northwest before transferring eastward in New York State.  The coastal spreads a swath of rain northeast off of the Virginia coast and then impacts Southeast New England as it takes over as the dominant feature.  The coastal will intensify into a potent storm, with winds picking up in its wake...which means winds pick up here tonight and tomorrow.  However, because that energy transfer from the northern energy to the coastal is not taking place fast enough, a dry slot of sorts is knifing northeast through parts of the region.  The result is less precipitation over us -- a general malaise of snow, drizzle, and mist for the city and points southeast with steadier rains confined to the coast while steadier and more substantial light snows are to the northwest.

We're still of the mindset that an inch or so of wet snow falls in the city -- not all of it may stick -- but it's enough to get something out of today.  North and west have a shot at getting a couple of inches of snow, perhaps 3" towards I-78, with 3-5 in the Poconos and across North Jersey.  South and east of 295 does not look good for much...generally less than an inch with drizzle and light rain falling.

We'll keep an eye on things through the day and update off and on as appropriate.  Unfortunately for snow lovers, it's not looking as good as it was 24 hours ago.