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Late Week Accumulating Snow

by Ben Pine

WHAS11.com

Posted on January 3, 2010 at 6:26 PM

We finally have a good chance of a few inches of snow around Kentuckiana next Thursday and Friday.  I want to talk a little about the basis of that forecast.   First , we need to determine the snow ratio (amount of snow per liquid water).  Most of our weather models forecast precipitation in the liquid form, and then we make the judgment where it will actually fall as snow, ice, or rain.  Over the next week temperatures will remain well below freezing throughout the depth of the atmosphere, so snow is our only option.  With that said...more on the snow ratios.

Near freezing (28-32 degrees) for every one inch of liquid water, usually 8-10 inches of snow will fall.  We call it a 10:1 ratio.

With temperatures colder than that the ratio goes up.  From 20-27 degrees, the ratio is now 15:1.  Fifteen inches of snow for every one inch of liquid.  So, if you melted that 15" snowfall, it would be an inch of water. 

From 15-19 degrees, it's a 20:1 ratio.

Next Thursday and Friday our temperatures will likely provide the 15:1 ratio.  The weather models are now giving us about .25" of liquid equivalent.  That amounts to 3.75" of snowfall for Thursday and Friday.  So, as the forecast stands now, we could see 2-4" of snow.  As we often say though, it's early, and the forecast is subject to change.

 

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