Wednesday, January 29, 2014

Snow Rollers- A Unique Weather Phenomenon

The weather this week has been fascinating and very changeable.  There have been  rapid changes in temperatures and lots of snow.  But the most interesting thing that I saw was the very rare phenomenon called 'snow rollers'.

Field covered with snow rollers

I had never seen or heard of a snow roller before they appeared here on the farm yesterday.  Normally our fields are smooth or gently drifted.  But this is what we saw yesterday.  Snow rollers form when you have wet packing snow followed by high winds that pick up the snow and roll it along the ground, kind of like you make a snowball for a snowman.  The wind has to be 30-40 mph.  Any harder,  and it just blows the snow around, any lighter and it can't lift the wet snow.  We had an unusual temperature rise during the night to 39 degrees F (3.9 C) which made the snow very wet.  There was then a sudden drop in temperature to about 16 F (-8.9C) and high winds.  That is what formed the 'Snow Rollers'.

If the Snow Roller was formed to face across the wind, then the center would be blown out and it would look like a donut or an eyeball.  That was pretty strange.  There was a number of these.

Paul went out and brought one of the larger snow rollers for us to look at.  You can see the layers of snow that were rolled up.  This roller was about 18" in diameter and was quite heavy.  The outside of it was icy and hard.

Professor Tony Vega has taught earth science at Clarion College for twenty years, but it’s the first time he’s ever seen snow rollers. He says conditions have to be just right for this phenomenon to appear.
“When the snow is perfectly wet, but not so wet to be heavy, the wind will pick it up and roll it,” he says. “And then it literally will snowball as it rolls across the surface.”

Here is a picture of the same snow roller from a different angle.  You can see where the wind was working on hollowing it out.

The sight across our fields was just strange.  Almost like a moonscape or a place where giants had a snowball fight.

Snow rollers, something it is unlikely that I will ever see again in my lifetime!  I am glad that I got to experience them at least once though.

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