Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Polystyrene Foam-like Snow
Name: Jackie
Status: other
Grade: other
Location: NE
Country: N/A
Date: 11/29/2005


Question:
A few years ago we had a thunder snow storm. The snow that fell was like polystyrene foam when we walked on it. What causes that kind of snow? I could walk on it and I barely made my footprints in it. It was really cool though and that was the first and only time I have seen that.


Replies:
Jackie,

You are describing could have been either graupel or soft hail.

Graupel occurs when snow falls from a cloud and then through warm air below the cloud. The points of the ice crystal melt forming a little ball of snow. More wetted snow can accumulate on the little ball and it can become a much larger ball of snow.

Since there were thunderstorms at the time, what you saw may have been soft hail. Soft hail forms in somewhat warmer conditions and in shorter thunderstorms than occurs in the summer. Since the temperatures in the thunderstorm are not extremely cold, the hail can partially melt and then accumulate more water (or even ice crystals) as it travels up and down in the cloud, eventually becoming too heavy for the cloud updrafts to support and falling out as soft hail.

David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory


Click here to return to the Weather Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory