My Favorite Ice Crystals


The best ice crystals are obviously dendrites, but not because they are pretty and glisten and all that mushy emotional stuff. They are a great manifestation of atmospheric dynamics. Given strong vertical motion, high amounts of cloud water, and favorable temperatures, dendrites grow faster than other types of crystals. The favored dendritic crystal growth range is -12 to -16 degrees centigrade. The potential for high snow accumulations increases when the listed conditions combine in the same portion of the atmosphere. Forecasters use vertical cross sections and time sections of model data to see where strong vertical motion and favorable crystal growth temperatures overlap. Since dendritic crystals have a feathery star-like structure, they accumulate fluffier than other types of crystals, especially without strong winds to break up and sift the crystals. A strongly dendritc snowfall with big flakes and near calm winds occurred in Green Bay, WI on December 23rd, 2000. The result was 5.5 inches of snow from only a tenth of an inch of liquid. Granted this storm was extremely fluffy even for Green Bay but it illustrates one of the numerous factors a meteorologist must consider when forecasting snowfall amounts.

What does this discussion of dendrites have to do with Duluth Local Influences? Not much really, especially since the example given is from Green Bay rather than Duluth. The author of this website wrote it while working as a weather forecaster at the National Weather Service in Green Bay. All ice crystals are great but dendrites are extra special. I like them a lot and so should you!


More information

"A Quick Review of Snow Microphysics And Its Relation to Heavy Snow Forecasting" - Greg DeVoir, NWS CTP Winter Weather Workshop, November 7, 2002 (view presentation)

"How Much Snow Will Accumulate" - A discussion by the author of this website (view)

All you wanted to know about ice crystals, snowflakes, and beyond - SnowCrystals.com