Major Combination Sleet/Ice/North Country
Never before in April, at least since records have been kept at Albany dating back to 1874, has there been an ice storm of the magnitude of the event that occurred from April 3rd to the 5th. It was a historical combination of snow, sleet, and significant accumulations of ice that brought down thousands of trees, limbs, and power lines throughout the Mohawk Valley, Capital Region, and northern Berkshire County over an extended period of time. Ice covered roads contributed to hundreds of automobile accidents Thursday night through Saturday morning. 275 schools closed Friday morning due to the extremely hazardous travel conditions. Across the north country counties of Hamilton, Warren, northern Saratoga, northern Washington in New York, and northern Bennington, and Rutland counties in VT it was a major snow storm that produced between 12" and 18" of snowfall over the three day period ranking the event as one of the heaviest snow makers of the entire 2002/03 season for those counties and among the largest April snowstorms on record. South of the Capital Region, from southern Schoharie, Greene, Columbia, and southern Berkshire county, MA on south, air temperatures through the majority of the event remained above freezing and precipitation coverage and intensity was generally much lighter than what occurred further north. Therefore, few problems developed in areas just south of the Capital Region.
It is not unusual in early April for wintry weather to occur. However, ice storms, especially ones of this magnitude are unusual. It is rare for ice storms to occur in April because a sufficient supply of low level cold air is typically very difficult to achieve due to the high sun angle moderating cold air masses very quickly. In this case, however, an unusually large and very cold Canadian high pressure system developed near Hudson Bay. A zonal jet stream flow, stalled over the U.S. northern tier of states, allowed only modest movement of the high pressure system, keeping it locked over southern Canada, in prime position to deliver cold air to the Northeast. Because of the configuration of the jet stream flow, cold air could only make it into the northern tier of states setting up a stationary front that extended from Iowa through the Midwest to northern Pennsylvania. North of the front a shallow layer of sub freezing air existed. South of the front, an unusually warm air mass featuring day time temperatures in the high 70s and 80s existed. The temperature contrast helped initiate areas of low pressure that tracked along the front, passing south of New York through the week. The passage of each subsequent low, moving along the front, induced a northerly flow of air over the Northeast allowing the shallow layer of subfreezing air to seep south into the region by Thursday, April 3, setting the stage for the ice storm.
ANATOMY OF AN ICE STORM: Ice storms form when only a shallow layer of sub freezing air, sometimes as thin as 500 to 1000 feet, air exists near the ground. The air above the subfreezing surface layer is warm enough to melt the snow that forms high up in the atmosphere into rain as it falls to the ground. That rain then falls on surfaces that are below thirty two degrees freezing on contact, causing ice to build up. If the rain falls over a long duration, is of light or moderate intensity, and there is a continuous supply of low level cold air flushing into a region, then significant ice accretions occur producing an ice storm, as was the case with this storm.
SLEET forms when the layer of sub freezing air near the ground extends up into the atmosphere several thousand feet producing a deep enough sub freezing layer to allow falling rain to freeze into ice pellets before that rain hits the ground. Sleet is the best case scenario precipitation type in an ice storm situation as sleet does not accrete on surfaces.
SNOW forms when the entire column of air from the ground to the level where the precipitation is forming is below freezing. In this case, a deep layer of sub freezing air existed over the north-country allowing mostly snow to occur over the three day period. The depth of the cold air fluctuated in the Capital Region over the three day period allowing periods of both sleet and freezing rain, with some snow as well.
The first round of significant freezing rain came in Thursday night, April 3rd. Ice accumulations of ½" were common through the region by Friday morning, April 4. Up to a foot of snow had also simultaneously fallen in the north-country where the cold air was much deeper. The gradient of no snow to heavy snow was very tight ranging from no accumulation at Clifton Park in Saratoga County, to 2" at Saratoga Springs, to 5" at Edinburg, to 10" at Glens Falls by Friday morning. Periods of light freezing rain and freezing drizzle and light snow across the north continued through Friday. By Friday evening, the layer of cold air over the Capital Region deepened slightly, allowing for freezing rain to mix with and change to sleet and snow, as several installments of heavy precipitation came through, through the night. The period of sleet and snow prevented a catastrophic ice storm for the region as ice accumulations would have averaged 1.25" to 1.75". As it was, total ice accumulations ranged from ½"-1" through the region, by Saturday morning, with north-country snowfall between 12" and 18", which was sufficient to produce widespread damage to trees and power lines. The counties most impacted by the ice storm were Fulton, Montgomery, Schenectady, northern Schoharie, southern Saratoga, Albany, Rensselaer, and northern Berkshire. Icing was not as heavy in southern Schoharie, Green, and Columbia counties. And very little icing occurred further south in Ulster, Dutchess, and Litchfield counties.
Inclement weather in the form of light freezing rain, freezing drizzle, and sleet continued through the day Saturday, April 5. Precipitation, however, was light and scattered enough to not substantially add to the already heavy ice, sleet, and snow accumulations. The jet stream, after a week in the same position, finally shifted south enough by Sunday, April 6 to allow the entire weather system to move far enough away to allow for the first sunny day in over a week. However, temperatures remained far below normal, only reaching the low 30s during the afternoon. Gusty winds, Saturday night and Sunday, resulted in more trees and power lines coming down, creating scattered power outages throughout the area all weekend. Power was not fully restored to all areas until Tuesday evening, April 8.
for the April 3-5, 2003 Storm
Town By Town Snowfall/Sleetfall Measurements from WeatherNet 6 For the April 3-5, 2003 Event
Ice Storm Photographs from Niskayuna
and Clifton Park