A multi-wave winter weather event is increasingly likely to unfold during the early to middle part of next week across a large majority of the Northern 1/3 of the United States, initially in the Great Lakes and then northeastward into New England. The exact area where this winter weather potential sets up obviously remains highly uncertain. Forecast models have been extremely inconsistent in handling mid and upper level features which will eventually have major impacts on the sensible weather experienced by many. But in this case, there are clues in the meteorological pattern that point to the answers to some of our questions. Instead of looking specifically at forecast models and their trends, we can begin to look for answers to our questions in the hemispheric pattern.
The winter weather threat traces its roots back to the total degradation of the West Coast ridge and positive PNA on along the West Coast of the United States into British Columbia. Inherently, this is a bad sign for snow lovers on the East Coast Any time we degrade a PNA ridge there is a positive mid and upper level height field response to the east of that over the Southeastern United States. In fact, the collapse of a PNA ridge can bring a response all the way into the Western Atlantic. As the amplified pattern out west collapses, the mid level jet collapses east into the Untied States and allows for the flow to enhance further to the east. So not only does the Southeast Ridge suddenly gain amplitude, but the pattern becomes more progressive over the Great Lakes and Southeast Canada — working against snow chances in the East.