Winter '12 / '13 - Siberian Express

The ECMWF has been advertising a significant cold intrusion into the lower 48 over the past few runs...along with a cross-polar shift of the polar vortex from Baffin Bay toward a position INVOF the south Kara Sea bordering northern Russia.

The yellow region on the map marks the location of 'warm' air at 100 mb.  This area is also where low heights in the troposphere are found.

This Siberian visitor should be enough to change the long wave flow regime just in time for the holidays.