AccuWeather Henry Margusity’s preliminary snowfall map for the witner 2011-2012 ( )

Here’s his reasoning:

The basis of the forecast [map above] is on the prediction that a weak La Nina will be forming this fall and continuing through the winter. Last year, we had a strong La Nina with blocking over Greenland that lead to a very snowy winter across the Midwest and Northeast. While the pattern will be similar to last year, there will be changes in the pattern that will lead to the heavy snow areas shown on the map.

I am not convinced that blocking will be prevalent across Greenland this winter, however, with the trough axis [dip in the jet stream] predicted to be in the Midwest, that will lead to storms developing along the East coast and racing northeast. The cold will be back in the Appalachians, and that will lead to heavy snow in that area. The major cities will probably be fighting many mix precip storms with the snow lovers along the I-95 corridor pulling their hair over heavy snow versus ice and rain.

I asked Matt Rogers, one of our long-range forecasting specialists for his reaction to Margusity’s ideas....

“Predicting heavier snow in the Midwest vs. the East Coast is consistent for expectations of a returning La Niña pattern this winter.  However, unlike Margusity, I do believe we will see strong North Atlantic blocking once more based on the unprecedented levels of the past few winters.  In these types of weak La Niña winters, we tend to not do as well with the number of snow storms, but we could get one big one yet (like 95-96).”

2:45 P.M. UPDATE: Capital Weather Gang’s winter weather expert Wes Junker just emailed me the following comment:

“Basically, I think it’s too early to make any definitive call about snow or even what the winter will be like. That said, La Nina climatology would argue for less snow than normal for the D.C. and Baltimore. The typical storm track is towards the Ohio Valley and Great Lakes with storms redeveloping off the coast to our north. That’s not a favorable track for the D.C. area getting more snowfall than normal as we’re on the warm side of the storm track. However, it only takes having the NAO go negative for a a couple of weeks and having one or two decent storms to put us at or above normal. Even in a year with the pattern being dominated by a storm track to our west, it’s possible for one big snowstorm to boost our snow totals above normal. That’s why forecasting snow in a seasonal forecast is a crap shoot at best.”

CWG’s winter outlook will be issued in the fall...