For one thing, we will get a reprieve from the sustained warmth which has plagued the region throughout November into the early part of this month. More generally speaking the teleconnection indices which have been quite disruptive particularly in recent weeks will also take a break There is no evidence of a decisive shift toward a "blocking" pattern of some variety, but a relatively neutral AO and slightly positive PNA will be just enough to at least get the ball rolling in the right direction. The first chance for significant snow is a very long shot. If it happens it will come from a wave of low pressure forming along the slow moving front to the regions south. If any real snow is to occur from this, the storm will need to intensify much quicker than what is currently indicated; otherwise, the storm will bring precipitation, and mainly rain to coastal cities.
A clipper system will arrive late Friday in advance of a much more substantial shot of chill, the first chance we will have of seeing temperatures lower than 10 F. A few inches of snow are possible from this before temperatures take this plunge. Thereafter, the pattern will be anchored by a classic La Nina style upper ridge in the Gulf of Alaska which is traditionally a dangerous place for such a feature. Thus, the risk remains for a early week warm up and non-snow type of event between the 12th and 14th of the month. Recent medium range model runs however have suggested that cold weather will grip a large portion of southern Canada and will keep us in the game so to speak. Any warm-up next week will likely be brief and my not occur at all. Cold weather will then overtake the region again after 15th and should grip the region for at least a 4-6 day stretch. It may not be a home-run forecast but at least an improvement over what we have seen.
Another positive development is the speed at which the Hudson Bay is freezing. Cold weather has gripped that region of Canada and that large body of water is on pace to freeze in a week to 10 days. This would be several weeks earlier than last year and will allow unmodified cold weather to move into eastern Canada a lot more freely. This is a critical thermal feedback that we will need to work in our favor if we are to proceed into the heart of this winter without any high latitude "blocking" to assist us.