Friday, December 21, 2012

A Punchers Chance of Boxing Night Ice Nearby

Besides the Christmas Eve Night event, the second and larger storm for Wednesday or Thursday of next week continues to loom as a potentially wintry storm system for the Mid Atlantic and Northeast. This may not be your traditional "rain and snow" type of storm -- computer modeling has shown a tendency over the past day or so to suggest that a wide variety of precipitation types throughout the region.

The key to this is the track of this storm system and the potential for a low pressure transfer to the coast from a primary low pressure track into the Ohio Valley before it runs into a high pressure block to the north.  This would then allow for low pressure to transfer east to a secondary center off of the coast, which would intensify in the Atlantic.

This primary low may be a bit too strong to prevent the city from being too terribly snowy with this second storm.  However, the combination of relatively cold air around the region on Christmas Day and the 26th plus the storm's low pressure track to our south will result in a relatively cold storm that will bring rain, snow, and in between precipitation types to the Mid Atlantic.

Modeling varies over specifics between the Euro and GFS, as it normally does this far out.  Like I typically say five or six days from a storm, details don't matter but the big picture does and it's worth talking about the potential for this storm as it approaches the region.  More importantly, the potential for a mixed bag of precipitation types.  As of now, it does look like some portions of the Mid Atlantic may see a decent snowfall -- both the GFS and Euro indicate the possibility for Central Pennsylvania and the Poconos.  In between there and the rain line, an area of icy rain or sleet may occur.


The reason for that is the presence of warmer air aloft pushing north around the old primary low pressure center while the surface low transfers on a track to our south.  This keeps colder air in place over the surface and very low levels of the atmosphere while temperatures farther aloft may be above freezing.  This isn't a certainty and the areas the GFS (map right above) or the Euro are indicating as the areas where freezing rain or sleet may occur may not ultimately be where this occurs.  We could see these areas shift northwest or southeast over the coming days as the storm approaches and the details come into better focus.  We also need to watch the impact of the first storm system with regards to reinforcing cold air into the region.

It's a busy pattern -- these two systems over the next week and a possible storm system for the 30th or 31st -- will definitely keep us on our toes.  Stick here as we update the upcoming storm systems as they approach!