Southern AER

A Quarterly Activity Bulletin of The South Carolina Department of Natural Resources-Southeast Regional Climate Center
Winter 2000
Volume 6, No. 4

How does snow form?
Snow crystals form when a cloud precipitates and the temperature is at freezing or below. Just as rain forms when water molecules collect on dust particles within the cloud, snow forms as well into partly melted crystals. These crystals accumulate and form snowflakes.

The Bergeron Process
The Bergeron process involves the exchange of molecules between water droplets in a cloud and an ice crystal. The ice crystal attracts water vapor molecules from the droplet, and grows in size. This is a part of the crystal formation process that makes snowflakes.
For more information on the Bergeron Process, click here, here, or here.

Where Snow Occurs
Snow is surprisingly not bound by a particular region. It can occur in any place as long as the air temperature falls to freezing or below and there is moisture in the air. For a map of us accumulated snowfall in the U.S., click on the Colorado State University Department of Atmospheric Science link here.

Snow Terms
Snow can be described in a variety of ways. Every region has its own terminology for snow and snow events. Identifying the "type" of snow that occurs where you live can be fascinating.

Snow Terms and Definitions
Word	Definition
Avalanche	mass of loosened snow, ice, and/or earth suddenly and swiftly sliding down a mountain.
Blizzard	a severe weather condition characterized by low temperatures, winds 35 mph or greater, and sufficient falling and/or blowing snow in the air to that reduces visibility.
Corn Snow	snow that looks like large, corn kernel size granules usually occurring in the Spring.
Flurry	snow from a convective cumulus- type cloud and characterized by the suddenness with which they start and stop.
Freezing rain	rain that falls as liquid and freezes upon impact to form a coating of glaze on cold surfaces.
Frost	covering of ice crystals that forms by direct sublimation on exposed surfaces whose temperature is below freezing.
Graupel	precipitation which looks like round pellets and is subject to rolling and can collect in pockets. It can also form a layer with a great deal of pore space and poor bonding. The pellets themselves are snowflakes which accumulated rime ice as they fell through certain atmospheric layers.
Hail	precipitation that originates in convective clouds in the form of balls or irregular pieces of ice and comes in different shapes and sizes, but must have a diameter of at least 5mm.
Hard Pack	when snow becomes firmly packed. Often snow that has never melted or recrystalized.
Hoarfrost	ice crystals formed when water vapor condenses directly into the solid phase onto a very cold surface.
Ice	hard, glazed surface created by freezing rain, rapid freezing temperatures and/or saturation from ground water seeping up into the snow and freezing.
Ice Crystals	slowly falling ice needles, columns, or plates. Make up cirriform clouds, frost, and ice fog.
Ice storm	severe weather condition characterized by freezing rain/ice. Forms a glaze on objects.
New Over	any accumulation of snow over an existing surface.
Packed Powder	snow that has been packed down and no longer fluffy, but not hard snow either.
Powder	cold, new, loose, fluffy dry snow that has not been compacted. Ideal for skiing.
Rime	supercooled water droplets which have frozen onto any surface.
Sleet	small bits or pellets of ice that rebound after striking the ground or any other hard surface.
Slush	snow or ice on the ground that has been reduced to a softy watery mixture by rain and/or warm temperatures.
Snowdrift	smooth rounded deposit of transported snow.
Wet Snow	snow that has become moist due to thaw/rainfall or had a high moisture content when it fell.

Links to Other Snow Terms
Inuit/Aleut Words
Snow Dictionary
Ski-Snow Terms

Snowflake Shapes
You may have heard that no two snowflakes are alike. That can be debated, but there are certain shapes that snowflakes tend into. There are several different classification schemes (click here to go to the Caltech page and read more), but the six basic shapes are: needles, columns, plates, dendrites, plate-capped columns, and irregular. A crystal's shape depends on the air temperature and humidity that occurrs while the crystal is forming. When it is colder, the snowflakes are smaller and when the temp is closer to 32° F, the flakes are larger.


Frosty Fun
These fragile flakes can be used for things other than building forts, snowmen and sledding. They can also be part of a well-balanced diet! Below are links to interesting recipes that go beyond simply eating a handful of the fluffy white stuff. IMPORTANT: make sure you use clean fresh snow when you try these.

Snow Ice cream

ACTIVITY
Question: When was the first snowboard invented?
Answer: Nineteen _ _ _ _ _ _ _ _ _ _ .
Go through through the maze and identify what each picture is. The picture will correspond with a term from this lesson. Write the term in the appropriate blank below. When you finish the maze, you will see the answer to the question above spelled out in the boxed letters.

HINT: you may have to backtrack to hit all of the pictures

For more about snowboarding and its history, click here.

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Southern AER
Southeast Regional Climate Center
SC Department of Natural Resources
1201 Main Street, Suite 1100
Columbia, South Carolina 29201

The South Carolina Department of Natural Resources prohibits discrimination on the basis of race, color, sex, national origin, disability, religion, or age. Direct all inquiries to the Office of Human Resources, P.O. Box 167, Columbia, SC 29202.