I will give a synopsis of what I expect from Friday’s storm today and give a more complete forecast tomorrow….
So you don’t hold your breath through all the scientific mumbo jumbo, it looks like Berkshire County will get at least 8-12″ of snow and as much as 2 feet in the east facing slopes of the elevated terrain (watch out Savoy, Windsor, Peru, Otis and Becket) beginning early Friday morning, probably near daybreak, and winding down sometime early Saturday morning. Because of the strong northeast winds associated with this storm I think there may be some “downsloping” effect so that western portions of the county should get less than the elevated eastern terrain.
There will be two disturbances in the jet stream, one in the northern, polar front branch and one in the southern, subtropical branch which will merge over the Mid-Atlantic coast Friday and Friday night to create prodigious upward motion in the atmosphere and generate deep surface low pressure just off the coast. In addition, the southern disturbance will bring large amounts of moisture (water vapor) to the storm off the Gulf of Mexico and Gulf Stream. There will also be considerable environmental instability due to the warm Gulf Stream at the surface and cold air moving in aloft associated with the northern branch disturbance. There will also be a strong, cold anticyclone (surface high pressure) over eastern Canada. This will serve to increase the pressure gradient between the high and low so that northeast winds will become quite strong. It will also provide a plentiful supply of cold air near the surface so the precipitation should stay snow in most locations in New England. These are all the ingredients necessary for a very strong “Nor’easter”. Of course, this is based upon the presumption that all of these ingredients will come together at just the right time. With the coastal storm still 48 hours away there is still some uncertainty, however, I have a fairly high confidence level given the trends in the models, that this will be a big storm for New England. In particular, the European model (ECMWF), which has done the best with these coastal storms, has been consistent with its solution of a very deep coastal surface low located just off the east coast. The other models are now beginning to coalesce around this same solution. Snowfall totals could even be historic, between 2 and 3 feet in some portions of eastern New England, particularly in southeastern areas. There may be a mixture of precipitation types in the immediate coastal areas, but most places should stay all snow.
The timeline will look something like this…..A weak surface low pressure system will develop along the North Carolina coast in response to the southern jet stream disturbance while a weak surface low forming in response to the northern disturbance moves eastward across the Midwest in the early morning hours of Friday. It appears that the snow should begin in Berkshire County sometime near daybreak Friday but should be light through the morning hours. I expect only on the order of 1-3″ by early afternoon Friday. During Friday afternoon the jet stream disturbances will begin to merge and the coastal low will take over and intensify rapidly as it moves north-northeast up the coast, centered east of the Del Marva Peninsula during the afternoon and just south of Cape Cod Friday evening. The snow should become moderate to heavy as Friday afternoon wears on. By dinnertime my best guess is that most places will have accumulated in the 6-10″ range. The heaviest snow should be late Friday afternoon through Friday evening. The snow should begin to lessen sometime after midnight on Friday and end sometime Saturday morning as the surface low drifts eastward off the coast.
My best “guess” at this point (believe me, it is still a guess this early with a complicated coastal storm) is that total accumulations will be between 8-16″ for most locations, with 1-2 feet in the elevated terrain to the east. It is likely that there will be some “jackpot” locations (you know who you are) that will receive over 2 feet.
I will update this forecast tomorrow afternoon…