. . . SATELLITE AND SOUNDINGS

. . . A sounding released from Y62 at 0000 UTC on 10 Dec shows the air mass several hours prior to the beginning of the west-northwesterly period of lake effect snowfall. Note that the entire temperature profile at this time is much colder than the relatively warm temperature range where both capped columnar crystals (which grow in the warmer, columnar regime), and dendritic snow crystals form (crystal habitat figure from Byers, 1965).

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. . . These two types of ice crystals are important to the production of heaviest snow in many LES events. Both crystal types form most efficiently at temperatures near -15C, or warmer, and both provide efficient 'seeds' for graupel (Krauss, et al., 1987). It is heavily-rimed graupel (which usually appears soft and sticky) that characterizes the most common type of heavy LES snowfall -- that having deep convection and strong updrafts. Dendrites can also produce heavy snowfall accumulations in LES events characterized by shorter, multiple bands, and in shallower convection with weaker updrafts.

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