Why Didn't It Snow?

Many forecasts called for snowfall across Texoma during the weekend of November 23-25, 2013, but most of us saw freezing rain.  What happened?

It's all about the air above Texoma not the moisture.  Moisture reacts to the atmosphere around it and the temperature that it falls through. 

If the temperature is at or below 32 degree Farenheit when the moisture forms it will crystalize into a snowflake.  But of course we all know that there are different types of snowflakes and depending on the temperature when the moisture crystalizes determines the type of snowflake that forms.  Now to stay in the form of a snowflake all the way to the ground the snowflake needs to fall through air, all the way to the ground that is constantly at or below 32 degrees.

So let's think of the atmosphere above Texoma as a three layered cake.  For snow to form and fall to the ground in Texoma all the layers of the cake would need to be temperatures at or below 32.  And most of the computer models indicated to us that all those layers would be at or below 32 degrees on Sunday and Monday which means we would get snow.  In reality that wasn't the case and therefore the snow never really showed up, at least not in Wichita Falls.

In western Texoma all the layers of the atmosphere finally reached 32 degrees and counties such as Jackson, Hardeman, Foard and portions of Wilbarger saw snow Sunday and early Monday.

But here in Wichita Falls we got freezing rain the entire time.  Let's go back to the layers of our cake.

In our make believe cake over Wichita Falls only the bottom layer had temperatures that were at or below 32 degrees.  The middle and top layers were above the freezing mark and that means that in those layers of the cake, or air, the moisture was in the form of rain.  So rain falls from the cloud through the top layer of the cake where there was 'warm' air of temperatures of 33 degrees or higher.  Then the raindrops fell into the middle or second layer of the cake or atmosphere and there as well the temperature was 33 degrees or warmer so the moisture was still in the form of rain.

Now the raindrops fall to the bottom layer of the cake/atmosphere which was at the ground level and this is where the temperature was 32 degrees or lower.  Well, the raindrop has momentum and is moving rapidly thru the layer of air below freezing but it doesn't have time to freeze or crystalize so it becomes what we call 'super-cooled.'  This super-cooled rain then hits objects that are below 32 degrees such as trees, power lines, vehicles and roofs.  It's at this point the raindrop makes impact on those items and freezes on impact.  That is how we get freezing rain.

So what went wrong this weekend?  Well it is simple.  Our computer models, forecasters at the National Weather Service and ourselves thought that all the layers of the cake, or atmosphere would become cold enough that all three layers would be below freezing and we would see the moisture crystalize in the cloud and fall as snow.  But that didn't happen.

Through the entire length of the event the top layers of the atmosphere were above freezing except the bottom layer which was below freezing and we constantly got freezing rain or ice.

So that explains why we didn't get the snow we were expecting.  But it leaves open another question...what is sleet?

Sleet is when the top layer of the cake has temperatures above freezing and the moisture forms as rain.  That rain then falls into the second layer of the cake or atmosphere but in this layer the temperatures are at or below 32 degrees, freezing.  Once again the water becomes what we call "super-cooled."  The "super-cooled" raindrops keep falling through the layer of air that is below freezing but once the raindrops reach the bottom layer that is also below freezing, it has been falling long enough without coming into contact with anything that the raindrop begins to freeze itself.  When a raindrop freezes it doesn't crystalize, that only happens in the clouds.  So the frozen raindrop forms a small ball of ice, otherwise known as sleet.  And often once the sleet reaches the ground it bounces.

So that is the difference between rain, freezing rain and sleet. 

KFDX Meteorologist Bryan Rupp

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