A snow storm in New Mexico brings a variety of reactions to local residents. The ski hounds dust off their skis and hope for inches of powder. Students anticipate school closures. Homeowners start searching for their shovels and weather nuts get out their yardsticks to measure the depth. Becky Ramotowski of Tijeras does something a little different - she takes her camera outside in hopes of photographing a snow flake before it breaks or melts!

Becky captured an image of this snowflake with her digital camera during the first snowfall of the 2006-2007 winter season, in late November 2006. This snowflake is an example of a "stellar dendrite" and has a shape most commonly associated with snow. However, snow crystals come in a variety of structures including plates, needles, hollow columns and solid prisms.

While the structures are different, snow crystals are all based on hexagons, because water molecules bond only at 120 degrees. A snow crystal is formed when water vapor in a below-freezing atmosphere is deposited on a ice nuclei. Initial growth is generally in the shape of a hexagonal prism. Branches or arms develop at the 120 degree angles of the hexagon.
The type of crystal that forms depends on the temperature and relative humidity of the air. Dendrites are common at temperature between -12C and -16C, while plates form at both colder and warmer temperatures. Shapes are more simple with low relative humidities and more complex at higher relative humidities.

Becky photographs the snowflakes by hand holding a small 10x field loupe in front of her digital camera lens. She waits for non-broken flakes to land then quickly takes a photo. Dark surfaces are best for contrast, but it is important to select a material that does not stay warm, because a melted flake doesn't make much of a picture! For the photo above, a black nylon umbrella was used to catch the snowflakes because the fabric remains sufficiently cool. Wind can break the flakes, or cause them to "clump" together, so Becky waits for snow events with light winds.

This snowflake is not native to New Mexico - Becky photographed it in Bryce Canyon in 2004. This 12-armed beauty started out as a capped column (picture a snow crystal shaped like a spool of thread or a sewing machine bobbin). As the capped column moves into a temperature regime which supports plate growth, plate crystals start to grow at each end of the column. In this case, a dendrite grew on each end of the column, but the column formed with a 30 degree twist, making two plates with 6 points look like one flake with 12 points.
Interested in learning more about snow? Check out:
Want to monitor snow cover across New Mexico or any other area in the U.S.? Check out the interactive map page of NOAA's National Operational Hydrologic Remote Sensing Center.

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