Christmas Day Severe Nor'easter
The tremendous amount of snow produced by this classic winter storm is going down into the record books at Albany as being among the top ten largest dumps since records began in 1885. An official storm total of 21 inches was recorded at the CESTM building on the SUNY campus in Albany making it the 9th greatest snowfall on record in any month for the city. The 21 inch amount was also sufficient to rank the storm the 4th largest in December. And the 19.2 inches of snow that fell on December 25 smashed the previous Christmas day record snow at Albany of 11.8 inches which fell in a large storm in 1978. Snowfall amounts climbed to as high as 36 inches in parts of southern Herkimer and Otsego counties with widespread reports of 20"-25" in a zone that extended from northeast Pennsylvania, through the Catskills, Mohawk valley, Capital/Saratoga, regions to southern Rutland and Bennington counties in Vermont.
Snow began as light intermittent patches between 6:00am and 8:00am across much of the area. Generally light snows occurred through much of the region through the mid to late morning hours with a gradual increase in coverage and intensity by noon. Initially a period of sleet and freezing rain occurred in the mid Hudson valley to Berkshire county, MA during the morning. Lighting and thunder occurred in the area of mixed precipitation as low pressure began rapidly intensifying along the coast. With the storm exploding east of New Jersey bands of exceptionally heavy snow began forming and rotating northwest away from the storm center through the area between 1:30pm and 9:00pm. Snowfall rates climbed to between one and two inches per hour over much of the region with a periods of up to incredible five inch per hour snowfall rates. The most intense snow band cranked snow out at five to six inches per hour during the late afternoon and evening over the Catskills and Mohawk valley during the late afternoon and evening. That band of blinding snow pivoted through the Capital Region during the evening and eventually ended up in western New England between 8:00 and 10:00pm in a somewhat weakened form. By midnight snowfall rates decreased to an average of 1/2" per hour in patches. By 4:00am all but the last of the flurries had ended in the area leaving one of the most widespread deepest snowfalls in this area since the March 1993 blizzard. Although, winds did gust to 35 mph with this storm creating widespread blowing and drifting snow as well as whiteout zero visibility conditions, the duration of the wind and poor visibility was considerably shorter and less severe than what occurred in the March 1993 storm.
This storm, like most of the weather systems to affect the Northeast this season to date originated in the very active southern jet stream branch. (A moderate El Nino condition existing in the equatorial Pacific, where warmer than typical sea surface temperatures exists, leads to an enhanced sub-tropical jet stream and thus stronger than normal southern jet stream branch storms.)
The storm originally developed over the southwest U.S. as an upper air system on Saturday, December 21. This parent upper air storm, driven completely by the powerful sub tropical jet stream, then pulled out of the southwest over the weekend producing a surface area of low pressure over south Texas Monday afternoon. Warm moist air riding north ahead of the system in concert with the powerful jet lead to several episodes of violent thunderstorms over south Texas and the gulf coastal region as well as Alabama, southern Georgia, and Florida from Sunday afternoon through Tuesday morning, December 22-24. By late Tuesday, the primary surface low tracked northeast into the Tennessee river valley with a weak low forming along the mid Atlantic coast. This weak low shot out to sea south or our region but did produce some very light snow and flurries across southern New England Christmas eve. By Christmas morning, the primary surface low responsible for the heavy rains and severe weather outbreaks across the Gulf coast, and a swath of 10 inch snows across Missouri, southern Illinois, and Ohio, had moved into western Pennsylvania in a weakening state. This storm's energy was transferring to the coast, where the low that became the severe Nor'easter for this region, was forming. Explosive storm development occurred along the New Jersey coast during the Christmas morning and afternoon as the upper air storm interacted with the temperature contrast zone along the coast and strong jet stream winds, to cause a rapid expansion of rain near the coast and snow over the central New York and northeast Pennsylvania.
As the storm began it's rapid intensification along the coast, at one point deepening by a huge 10 millibars per hour, enough mid level warm air circulated into the mid Hudson valley and Berkshire county to allow a several hour period of mixed snow, sleet, and freezing rain to occur. However, the rapid accent of air in the atmosphere as the storm bombed out more than sufficiently created an environment of local cooling to allow the mixed precipitation to change to heavy wet snow. The interaction of ice and water as well as strong accent in the atmosphere, helped to create some lightning and thunder through the morning in the zone of mixed precipitation. (It is not unusual for lightning and thunder to occur in association with rapidly deepening winter storms.) Snowfall rapidly expanded in coverage and intensity after 1:00pm. Several banded features developed with the storm and pivoted away from the center into eastern New York and western New England through it's duration. Snowfall rates in the bands, ranged from two inches per hour to an incredible five inches per hour by the late afternoon and evening leaving tremendous snow accumulations ranging from 24-36" in the hardest hit regions of Otsego, Delaware, Montgomery, and western Albany counties.
The storm's structure was one of an extremely tightly wound compact system. The observed snowfall distribution map below illustrates how tight a system it was with a very sharp gradient of accumulations in the region. Notice how narrow the zone of heaviest snow was across eastern New York and western New England and how sharply the snow accumulations to the north and west of the blitz zone dropped off. (The slightly reduced snowfall amounts south and east of the Capital Region can be partially attributed to the period of mixed precipitation early in the storm and a somewhat removed position from the zone of maximum lift that set up with this system in the atmosphere.) It is not unusual for powerful storms of this nature to have very tight gradients of precipitation and is an example of how a forecast track error of as little as fifty miles can sometimes mean the difference between a few inches of snow vs. upwards of thirty inches of snow. The other interesting and somewhat unique feature of the storm was the rate at which the snow piled up. Most of the top twenty heaviest snowstorms at Albany occurred over several days . This storm, however, produced an average of two feet of snow through the Capital Region in an incredible ten hours!
As the storm deepened an initially NNE wind over the region shifted into the NNW and finally the NW and increased to 20-35 mph with gusts in it's wake over exposed mountains the following day to 45 mph. Temperatures through the duration of the storm held steady in the middle to upper 20's yielding a fairly dry, light snow, that was very susceptible to blowing and drifting. The blowing and drifting snow lead to particularly bad visibility with frequent whiteout conditions across the region through Christmas night.
Observed Snowfall Distribution Map For the Christmas 2002 Storm
(This graphic was created using snowfall data collected by WRGB's exclusive WeatherNet 6 weather spotter network as well as observations from the NWS cooperative observer network)
Town By Town Storm Totals from WeatherNet 6 Spotters and National Weather Service Cooperative Observers for the Christmas 2002 Storm