Let the fun begin! A major pattern shift will happen in the next 48 hours as a deep upper-level trough becomes established over the East Coast. This means cold air (highs will only be in the low 30s by midweek) and a better chance of snowstorms.

It's important to emphasize that this kind of cold outbreak does not necessarily mean a snowstorm. There are any number of other factors required for the "perfect storm," including jet stream placement and the position of the polar vortex over eastern Canada. Even once a coastal storm gets going, its path has to be just right--too far out to sea and we miss the boat; too far inland and winds turn to a warm easterly direction, changing snow to rain. Some on-air meteorologists have been hinting that next week may be "active," but this hype is premature.

What this cold outbreak does mean is that it's time to start the annual flurry of e-mail among weather geeks, analyzing computer model predictions, second guessing forecasts, and reporting obscure technical data that may or may not indicate that the big one is finally here.