Its moisture this storm has and its moisture that we most certainly need going into a very cold stretch of weather. The storm is the last product of a split in the Jet Stream and we expect some dramatic changes in the west over time which will act to dry out the overall pattern but also ensure that New England sits in the deep freeze for the span of at least a week. The short of it is that we need our January 7th storm to deliver this moisture and deliver it in quantities even if some of it does fall as sleet. By the looks of things we should get just what we need. The storm will gather copious (an old Weather Channel favorite) amounts of Gulf Moisture and proceed northeast in a very disorganized fashion. Storms such as this have often been referred to as "double barrel" but this system can be described as a discombobulated triple barrel storm with a clipper near Lake Superior, the Gulf low taking aim at Lake Erie while another system tries to form along the Atlantic system. It is this final system which will cut the warming off at the pass and ensure that precipitation falls mainly in the form of snow and sleet. This precipitation will begin prior to dawn Wednesday and continue as snow through the early morning before a period of sleet sometime during the day. This change to sleet is still uncertain and depends largely on the track of the storm and the speed at which the coastal low intensifies. Storms such as this can often have a "lull" during the warmest part of the storm when precipitation is very light. Following any sleet, we should see a return to snow as the lower atmosphere (or troposphere) becomes more favorable for terrain induced snow (upslope). It is therefore expected that we should see a second period of snow which will begin Wednesday night and continue lightly through the day Thursday. Overall the two days should see a much needed inch of liquid and 8-16 inches of a snow sleet mix. This will be a dense accumulation and it is this density which has the "staying power" Eric has been talking about on the board. Whew !!! That was a very long winded paragraph and not recommended for you aspiring journalists out there !!!
Some weekend snow and then the chill hits
Along with the light snow Thursday there will be a turn toward colder temperatures but this will pale in comparison to the week which will follow. The pattern will be undergo a massive structural re-configuration around this time and within a few days the dominant weather feature will be a stable upper level ridge in the western United States stretching north into southern Canada. This feature will take some of the brutally cold temperatures which have been covering the Yukon and send them toward us. As the pattern continues to amplify this weekend, a fast moving system will try and quickly grab Atlantic Moisture and deliver us some additional snow on Saturday. I am becoming optimistic for at least a few inches out of this and anything further will be a bonus. The bitterly cold temperatures will follow quickly on the heals of this system. As of now it has been the Upper Midwest which has felt the full force of the cold so far this winter but this will shift east after January 10th and we too will get a chance to get in on the fun.
I could be wrong in my interpretation and expectation but I expect the polar branch of the jet to be on the overwhelming side next week. This will suppress the storm track and limit the big snows. Clipper systems and terrain enhancement can still help to provide snow in some modest amounts if we are lucky. Cold it will be however as I could see temperatures failing to climb above zero for at least 2 of the 7 days following January 10th. There is some disagreement amongst the ensembles concerning any modification in temps for the back half of January but predicting a modification in temps from -15 is about as bold as predicting a trip to the bathroom after chugging 5 lemonades (I could say beer but I wanted to be family friendly).