A Case Study of Anomalous Snowfall with an Alberta Clipper

Abstract

An Alberta clipper moved over western New York state on 11-12 January 2004, producing snowfall amounts of up to 27 cm in portions of the region during a roughly 12-h period. In addition, lightning and thunder were reported. Such systems, known primarily for their fast motion and relatively dry nature, are not generally associated with significant snowfalls. A postmortem analysis of this event, following an ingredients-based methodology, revealed that as the weak low approached the lower Great Lakes, it came under the influence of coupled 300-hPa jets that produced enhanced divergence and significant upward vertical motion over western New York, resulting in the enhanced convective snowfall over the region for a limited time. Instability and possible enhancement via the Great Lakes are also investigated, which show that while there was at least modest instability over the region during the time of heavy snowfall, lake enhancement was unlikely.