January 14-15, 2007
An arctic boundary moved southward across the region Saturday and stalled over the mid Atlantic region Saturday night. With the passage of the boundary, cold air was drawn in at and near the surface on northerly winds. Waves of low pressure moved eastward along the boundary over the long weekend.
A weak low passed to our south on Sunday resulting in periods of light freezing rain. However, the primary/deeper low moved from the Ohio Valley eastward across the local area Monday bringing heavier precipitation. The precipitation did start out as a period of sleet late Sunday night into early Monday morning with snow across the southern Adirondacks, however everything eventually changed to freezing rain.
Why freezing rain? At the surface there was cold air, but aloft warmer air moved in causing the precipitation to melt as it fell through the warm layer. Then, the rain drops hit the freezing objects at the surface and frozen on contact. Warmer air did work in at and near the surface in the Capital District region and to the south and east Monday afternoon and evening. Elsewhere, temperatures remained below freezing. The soundings from Albany show this evolution well.
Soundings from Albany NY:
Significant ice accumulations occurred with over 100,000 utility customers losing power. Saratoga County was hit particularly hard with up to an inch of ice and accounting for about half the power outages. Ice Accumulation Map
To make matters worse, winds increased Monday evening placing additional strain on the already burden trees and power lines leading to additional power outages even after the freezing rain ended.
The low deepened and moved off to the northeast across the Canadian Maritimes Monday night and Tuesday drawing arctic air across the region. By Wednesday morning, temperatures fell into the single digits to below zero.