WINTER PRECIPITATION

I can distinctly remember one too many a time, having half a foot of snow on the ground with heavy snow falling and a temperature of 27 F, only to have what was definitely a "Snow day"in the making get washed down the drain as snow turned to sleet, which then turned to freezing rain and then ultimately to rain. To top it off, the switch to sleet would occur with temperatures in the upper 20s. How dare the atmosphere! This used to drive me nuts! "How can it be sleeting", or worse yet... "How can we be getting freezing rain with a temperature below 32F!" I can also distinctly remember not having finished up homework because I thought we wouldn't have school... mistake.

So, how does this mixed bag of winter stuff form? It's just a matter of how much cold air is in place and the depth of the below freezing layer. On the left hand side of the graphic, the temperature is below freezing through the entire depth of precipitation. It falls as, and remains snow. This is the set-up that I am hoping for in a BIG WAY sometime this winter. Sleet forms when snow falls into a layer of warm air that is above freezing and then falls back into a layer that's below. With a sufficient depth of cold air the rain drop refreezes into a pellet of ice. Freezing rain forms in the same fashion as sleet, though the depth of the cold air is very shallow. The rain drop remains in a liquid state only to freeze on contact as it hits objects at the surface that are slightly below freezing, making a glaze.

On a side note... some of the best sledding that I've ever done was after a storm put down about a foot of snow, an inch or so of sleet and then about 3/4 of inch of freezing rain. We took metal runner sleds to the local Golf course and flew down a few par fives!

Posted by Ted Zarras at 6:30 PM