In all three snowstorms observations show band formation was coincident with the sharpening of a midlevel trough and associated increase in frontogenesis in an environment of elevated conditional, slantwise, and inertial instability. Conditional instability was greatest in the 12 February 2006 snowstorm, where lightning was observed with the snowband. In all three cases band dissipation occurred as the midlevel trough became more diffuse, weakening the associated frontogenetical forcing, while the stability increased. Changes in moisture availability in the banded region during the band life cycle were small, suggesting changes in the forcing and stability were the primary governors of band lifecycle in these three northeast U.S. snowstorms.
Band formation was forecast by high-resolution versions of the MM5 and WRF in all three snowstorms; however, a clear under prediction of precipitation was noted in the 25 December 2002 and 12 February 2006 snowstorms. Also, in all three snowstorms model forecasts exhibited band location and evolution errors. Possible reasons for these model errors will be presented at the workshop. Particular focus will be placed on differences between observations and model forecasts in the environmental stability and evolution of the midlevel flow in the vicinity of the bands.