Early and Late Morning Model Cycles show potential for storm late next week

A large snowstorm is impacting the upper Midwest/Western Great Lakes, where isolated amounts of up to 12" of snow can be expected in western WI and eastern MN.  A large comma head has developed with this system and heavy snowfall rates of 1-3"/hr is possible throughout today.  Ridging is taking place across the eastern US as well as over the western US where a large trough has been stationary the past week or so.  Temperatures will probably rebound into the lower 60s regionwide this afternoon across SNE as return flow from the south and southwest will bring warm temps northward admist strong warm air advection ahead of the occluded front that will try to progress eastward.  However given that the storm will become occluded at some point on Monday, the front will not make full progress to the coastline until sometime Wednesday, where strong tropical moisture transport ahead of the strong longwave trough, will produce a large area of moderate to heavy precipitation.  Pattern is progressive so no more then 1.5" of rain will fall in any given area.  Flooding should not become a major problem with some regular street flooding in low lying regions.  As the storm intensifies over the region and heads into the Canadian Maritimes return flow from the low will bring in strong cold air advection and will bring the air temperatures slightly below normal.  Strong northwest winds will be common on Thursday and will settle down come Friday as yet another shortwave trough disturbance comes through the mid level flow.  Models have been hinting at a slight, short-lived pattern change in which the NAO heads towards negative and the persistent +EPO the last few weeks breaks down as a strong mid level trough enters the NE Pacific Ocean.  This will in turn, allow ridging to develop out ahead of it over the western US.  The flow over the Pacific and western North America is progressive so the ridging will be short lived.  However the -NAO and -AO coincide with a slight positive PNA ridge present as a clipper system drops out of Canada into the central US Plains.  Models are in two camps: the progressive out to sea camp of the 00z EURO/12z GFS which show a frontal passage followed by cold air advection into the region from northwest winds as a large low pressure center is present over the Canadian Maritimes.  The second camp involves the 12z NAM/00z GGEM and to an extent the 00z/06z GFS ensemble means.  While the NAM does not reach this time table for next Friday, the NAM offers a few suggestions to what could possibly come out of this system just from hour 84, of the short range model.  One thing is for certain and that is the NAM is stronger with the secondary shortwave trough then the 12z GFS has been which leads to better chance of amplification of the shortwave.  The GFS is progressive as well as strung out with the mid level energetic disturbance and does not allow secondary cyclogenesis to take place.  It looks to be a mainly rain event, unless future model runs bring the 700mb/850mb circulations further south, more so south of the SNE South Coast.  Western CT, MA and VT could see some accumulating snow from this system if the current models are right.  The GGEM is the most robust with secondary cyclogenesis as the storm deepens down to the lower 980s just south of Martha's Vineyard, MA.  Chances are we would see rain initially over the coastal plain followed by a changeover to potentially accumulating snow over eastern MA if the 00z GGEM is correct.  However we still have a lot of time in weather forecasting before this system becomes a threat.  Precipitation chances occur on the 16-17th and 18-19th.  Still some time to decide the details, but the pattern is favorable for at least rain/snow showers.