The winter season 2002-2003 brought three absolute blockbuster storms to the Northeast with the 9th and 10th heaviest snowstorms on record at Albany occurring within eight days of each other on Christmas day, then again immediately after the New Year. The President's day storm in February 2003 brought more very heavy snow with several other noteworthy storms bringing moderate to heavy snowfall to the region. A strong and consistent jet stream pattern featuring a very active low pressure trough in the east was responsible for the repeat blockbuster storms in the 2002-2003 season. The pattern in the young 2003-2004 season, however, began changing in October, featuring more of a ridge in the east forcing large storms to the west of New York and New England and consequently bringing large amounts of rain. The pattern however, was not consistent, with many fluctuations. This lack of a pattern lock meant large snow storms could occur as the jet transitioned from one phase to the next. However, the number of large storms would be in question.
There was no question, however, that as the jet stream began a phase change the first week in December that stormy weather would occur. The question was how would the storm or storms manifest themselves and would there be significant snow for Northeastern part of the country? The answer, ultimately, was yes.
The scenario leading up to the major Nor'easter of December 6-7 was very complex. Several disturbances in both the northern and southern branches of the jet stream played key roles in the eventual development of several coastal storms that brought very heavy snow to the mid Atlantic and Northeast corridors. The first phase of the storm originated primarily in the southern branch of the jet stream. Low pressure on Thursday, December 4, began spreading rain and snow across the Tennessee and Ohio Valleys, and to parts of the Southeast. The initial storm was rather disorganized but nevertheless lead to a light to moderate snowfall for parts of the Midwest. This storm jumped to the coast where it continued to produce snow, moderate to heavy at times, for Virginia and the rest of the mid Atlantic to New York city through Friday, December 5. This storm would have continued an eastward track out to sea south of the Capital Region, keeping the region free of snow, had it not been for the presence of a strong upper air storm sliding south through the northern branch of the jet stream on Friday. This second disturbance brought more snow to the Midwest before merging with the coastal low that was continuing to bring snow to the mid Atlantic and New York City Friday night. The merging of the systems caused another coastal low pressure system to form early on Saturday the 6th, which became the primary storm. The system slowly strengthened and only slowly tracked to Cape Cod by 7:30pm on the 6th, then pretty much sat stationary through the early morning on Sunday the 7th. The storm track and associated jet stream structure over the Northeast was favorable for several bands of moderate to heavy snow to set up over upstate eastern New York and New England beginning around 1am on Saturday and continuing through the day and night, and into the day Sunday the 7th.
There was not to much remarkable about the Nor'easter in looking at the center of low pressure itself. The storm was fairly strong, but not as strong as many past storms. The system was strong enough to produce winds along the coast to between 35 and 45 mph on average. The wind did lead to blowing snow and occasional whiteout conditions, but nothing to out of the ordinary for a major east coast storm. The system was slow moving primarily because of the position and evolution of the parent upper air storm which moved to the coast essentially catching the surface system and slowing it down. The storm did eventually accelerate during the day Sunday, December 7 to bring snows to an end across eastern New York and western New England.
Snowfall accumulations across eastern New York and all of New England were very heavy, part due to the fact that the air was very cold allowing for a very dry, light, fluffy snow to fall. The average water to snow ratio was 14:1 in the Capital Region during the storm on Saturday, which simply means an inch of liquid equivalent water would produce 14" of snow. The ratio, however, jumped to 38:1 on Sunday, meaning an inch of liquid would produce 38" of snow. A standard water to snow ratio is around 10:1 to put these numbers into perspective. The 12.5" of snow that fell at Albany on Saturday was good for a 24 hour snowfall record for the day. 5.5" of snow fell on Sunday, the 7th, from only .15" liquid equivalent. The 5.5" of snow on Sunday was also good for a 24 hour snowfall record for the day. The total of 18" of snow at Albany ranked this the 7th largest December snowstorm on record and the 15th all time heaviest snowstorm on record at Albany.
The heaviest snow with the storm occurred late Saturday morning through early Saturday evening. Snowfall rates of 1"-2" per hour were common during this time. A very small scale band of intense snow, rates at times as high as 4" per hour, formed over the Hudson Valley, with Columbia and Rensselaer counties being particularly hard hit. Pockets of light snow, enhanced at times in the Capital Region by the Mohawk-Hudson convergence zone that sometimes sets up as storm's depart the region, continued into early Sunday afternoon. By Sunday mid afternoon, breaks of sunshine had developed in the region with some blowing and drifting snow as winds gusted at times to 30 mph in the wake of the system.
A bull's eye of over 30" of snow occurred in Rensselaer county centered on Averill Park, with much of the rest of the Hudson Valley area receiving anywhere from 17"-24" of snow. Snowfall ranged from 11"-17" across the vast majority of the remainder of eastern New York and Berkshire and Litchfield counties. Snowfall in Vermont, due largely to even colder air creating a greater "Fluff Factor", ranged from 17"-24" statewide. The mountain downslope effect, so often observed in the local area, especially in Washington and Bennington counties, with coastal storms, apparently was completely mitigated by the upper level mechanisms at work to produce lift in the atmosphere and therefore precipitation. The snowfall distribution for this storm shows no downslope effects as the heaviest snow was observed in the Hudson valley, rather than in the higher terrain to the east of the valley or in the higher terrain of the Catskills west of the valley. Part of most Nor'easter's ability to produce snow comes from the circulation of air around the storm's center. The air circulation around a Nor'easter typically interacts with the mountains to create higher snowfall amounts there, and lower snowfall amounts in the valleys downwind of the circulation. Typically that leaves the higher terrain east and west of the Hudson river as the jackpot snow zones with lighter accumulations in the valley itself. Since the reverse was observed with this storm it is safe to say that this was an unusual snowfall distribution.
(Snowfall Distribution for the December 6-7, 2003 Nor'easter. Storm Total Snowfall Observations from WeatherNet 6 and Albany National Weather Service Cooperative Observers were used to create this map.)
Storm Total Snowfall Observations for the December 6-7, 2003 Nor'easter