The dream is still alive for a possible early season significant snowfall across the Adirondacks, but it’s not in the bag yet. The potential storm is now showing on the shorter range NAM, with the players I talked about last week. This panel shows the blocking low offshore eastern Canada, the Great Lakes trough and the developing coastal storm by Wednesday evening:
The blocking low is key to this setup because it holds the developing storm near the coast long enough for it to phase with the digging Great Lakes trough. In other words, without the blocking low, the coastal storm would scoot out to sea before the Great Lakes trough can capture it.
NAM simulated radar shows a healthy nor’easter storm by Wednesday evening with precipitation beginning to spread into eastern New York:
The simulated radar snapshot may look as though the storm is headed out to sea. But as the Great Lakes trough captures the nor’easter Wednesday night, the storm’s center of circulation should track northward to around Cape Cod by Thursday evening, pushing heavy precipitation northwestward into the Adirondacks. UKMET shows a massive vertically stacked storm nearing the southeastern New England coast by Thursday morning:
A vertically stacked storm is one where the surface low pressure center is located under the upper air storm. This is usually indicative of a storm that has reached tremendous intensity and size.
Will this be a snow storm for the Adirondacks?
Even if the models are indeed correct on the development of this storm, the atmosphere on the western flank of this storm will only be marginally cold enough for snow. In this situation, the storm will need to generate precipitation at a sufficiently heavy rate to drag colder air down to ground level. In essence, the storm will have to manufacture its own cold air in order to support a snow storm, instead of a chilly rain. With this storm still at least 3 days away, it’s still a very open question as to whether the storm can manufacture enough cold air to tip the scales to favor snow.
IF this storm takes it to the house later Wednesday night into Thursday, there are several issues in regards to determining potential snow accumulation: precipitation intensity, elevation, ground temperature, and even proximity to warmer lakes. There could be wild variation of snow accumulation within a few miles or less. A significant accumulation of heavy wet snow could bring down trees and power lines.
The potential does exist for 6 inches or more of snow accumulation over much of the higher terrain in the Adirondacks. That is not my forecast YET, but this needs to be watched closely.
After that?
If we get the snow, don’t fall in love with it. A massive surge of bitter cold arctic air will plunge into the western United States, which in turn, will pump the warmth back up over the eastern United States. ECWMF is showing a flat out blizzard for parts of the Dakotas, Wyoming, Montana and Colorado by next weekend, along with the first widespread sub-zero cold for the Northern USA Rockies. The Pacific North Atlantic Oscillation will be in its negative phase (PNA-), so that cold blast in the west should retreat into Canada rather than spread all the way across the United States:
This link has a good thumbnail sketch on how the Pacific North American Oscillation works.
Then what?
October was wet with a total of 6.84 inches of rain at the Indian Lake Dam (over 3 inches ABOVE normal). It appears this trend may continue into November. The rapid buildup of snow cover over Canada and the proclivity for coastal storm development are encouraging. When the time comes for the snow to begin sticking for good, we may be off to a fast start this winter. 🙂
