For all of the non-mountain Mid-Altantic people out there, I’ll go ahead and say right off the bat that it’s unlikely we’ll see any snow from this event. If this system does develop, it will likely be cold rain throughout, with a slight chance of seeing some snow in the air (NOTE: not accumulating) early Saturday before the storm moves off to the northeast. The real target of this system is northern NJ, Upstate NY and New England.
So what are we looking at? The last couple of model runs from both the GFS and ECMWF are showing a coastal storm… one that is expected to form off the Carolina coastline Friday night into Saturday morning. Exact timing/placement of the surface low will be crucial in trying to get snow anywhere in the Mid-Atlantic. Should the development be too slow (as is often the case in thread-the-needle type events in the Mid-Atlantic), the low will form too far off the coast and will not deepen enough to produce much precipitation in the region. There is a small break between an earlier system and this system to allow for a weak area of high pressure to develop over the Canadian Maritimes, but it would be weak at best. This high pressure would help slow the storm’s eastward movement and allow it to develop closer to the coast. While not critical, it would be a nice feature to have in place if we want to get snow.
Furthermore, we are relying on upper-level energy from the northern stream (i.e. the energy behind that develops this system digs down into the region from the north as opposed to originating to the south). The system could be modeled too far south at this range, and a further north solution would not yield snow for us. Also, there really isn’t that much cold air available… we’ll be chilly, but it will likely stay above freezing in the lowest levels of the atmosphere, which would melt any snow before it gets the chance to hit the ground.
Should the low develop close to land, the eastern slopes of the Appalachians could see some accumulating snow in the higher elevations (at this point we’re looking at places above 1500 feet) if the precipitation can actually make it that far west.
Snow is very hard to get in October in the lower elevations this time of the year, so don’t expect to see much. If the Saturday morning snow threat is still viable in a couple of days, I’ll try to post an initial snowfall forecast Wednesday afternoon/evening.