Hurricane Sandy is likely to be one of those rare tropical beasts that produce snow. In the Mid-Atlantic region, southwest Virginia and West Virginia have the best chance of receiving accumulating snow from this storm. (It is not likely in the immediate Washington, D.C. area.)
Such a hurricane snow event would not be unprecedented. Late season hurricanes that transition to extratropical cyclones have been known to produce snow. The New England snowicane of 1804 hit the coast near Atlantic City New Jersey beforing recurving eastward and tracking across southern New England. It produced snow across portions of upstate New York and New England. Some location s reported over two feet of snow.
Ginny in in 1962 produce well over a foot in portions of Maine. More recently the remnants of Wilma produced snow as far southward and Pennsyvania and West Virginia .
Sandy starts off as a warm core, tropical system so as it come north it will bring lots of warmth with it. Below I’ve only shown the GFS model solution not because I think it’s right, but to display the thermal structure of the storm which is similar on almost all the models.
The strong easterly winds that set up to the north as it approaches will help wrap warm air around the north side of the low even as cold front shifts eastward to the south side of the storm. That keeps the cold air to Washington, D.C.’s southwest on all the model forecasts
The precipitation with tropical storms is typically heaviest on the east side of the storm where frictional convergence sets up near the coast. However, with transitioning storms the heaviest rain usually develops along the frontal zone that sets up as the storm moves north and east. Essentially, warm air moist air is lifted along the frontal zone where it condenses and fall out as rain.
Sandy throws a wrinkle into the typical system evolution as all the warm air wrapping around the storm essentially helps set up frontogenesis (development of a cold front) even on the south and southwest side of the storm. Both the European and GFS model runs show very similar structure and show a band of heavier rainfall to the south and southwest of the storm.
Snow is likely where the cold air is collocated with the western edge of the zone of lifting while there is still moderate precipitation. Both the European and GFS model solutions show the temperature (at approximately 5000 feet, 850 mb) cold enough for snow in this zone.
However, the location of this zone differs somewhat depending on how far north the storm tracks. Right now, the GFS - with its slightly more northerly landfall - allows the cold air to wrap into the storm a little farther north than the European model. However, even the European model suggests that any accumulating snow would be located over the mountains of West Virginia and possibly southwestern Virginia.
A further shift north might allow the cold air to get into the mountains of western Maryland and northern Virginia.
Based on the current most likely storm tracks, it looks like the mountains Southwest Virginia and West Virginia have the highest snowfall probabilities and may receive substantial snow over 12” at high elevations. Such heavy snow on top of existing foliage could cause tree damage and power outages. In western Maryland, the chances of heavy snow are somewhat less.
East of the mountains, mild surface temperatures significantly lower the chance of seeing snow. There is an outside chance of non-accumulating flakes towards the tail end of the storm if the landfall is far enough north and cold air is able to wrap around the storm enough.