The Effects Of Orography In Northern Vermont During The 2-3 January 2010 Winter Storm

A snowstorm on 2-3 January 2010 affected parts of the northeastern U.S. with significant snowfall and strong winds. Record single storm snowfall totals as high as 84 cm were reported in Burlington, Vermont with winds of 20-25 m/s. Despite uniform precipitation type in northern Vermont, total snowfall varied significantly over a 20-30 km stretch, highlighting the importance of orography and other mesoscale processes. This research uses a variety of observational and model analyses, as well as a high-resolution WRF simulation, to diagnose the nature of the low-level flow and the effect of the Green Mountains on the observed snowfall totals. The results of this study may help determine the primary mechanism responsible for the unusual displacement of heaviest snowfall well upstream of the Green Mountain spine.

This event was characterized by a cutoff upper-level circulation over eastern New England, with anomalous northerly mid-level warm-air advection in the equatorward exit region of an upper-level easterly jet streak over northern Vermont. A strong frontal inversion below the ridge tops of the Green Mountains and prolonged moist, northwesterly flow at low levels, led to orographic blocking in the eastern Champlain Valley. Sounding analysis indicates that precipitation microphysics were ideal for high snow to liquid equivalent ratios in the region of heaviest snowfall. The effects associated with Lake Champlain moisture, as well as the shape of the Champlain Valley, may have also affected the forcing for upward vertical motion in vicinity of Burlington, Vermont.