Storm Event Synopsis

February 21, 2013

 
 
 
 


A strong dynamic storm system affected the Missouri Ozarks into southeast Kansas mainly during the overnight hours and through the day on February 21st, 2013. This storm system brought a wide variety of winter weather including thunder, freezing rain, sleet and snow to the region.

Dry and cold antecedent conditions led to a later onset of precipitation in the Ozarks which began as snowfall.

From the 6 pm sounding above, you can see the very dry air (green is the dew point, red is the temperature) in the lower levels that had to moisten up before precipitation would reach the ground. The initial precipitation falling was evaporating in this dry layer but also cooling the air in this column via a process called evaporative cooling.

By the midnight sounding (above), you can see the mid levels of the atmosphere had moistened up quite a bit but it was still pretty dry (although moistening) in the lower levels.

There is a lot going on here in the final 6 am sounding shown above. First of all, notice that the low levels continued to moisten overnight. Warmer air above the surface was advected in from the strong south to southwest winds with temperatures up to 4 degrees Celsius (39 deg F) within the warm nose. The helped to melt the snow as it was falling from above and then fall back to the below freezing temperatures at the surface for freezing rain. There was also enough elevated instability above the warm nose of air to promote thunderstorm development within the precipitation. Sleet became heavy at times during the bouts of thunder during the day.

Eventually during the afternoon, drier air in the mid and upper levels of the atmosphere worked into the area from the southwest and helped push the bulk of the precipitation to the east. Some moisture wrapping around the low brought some freezing drizzle to the area during the evening into parts of the overnight hours of the 22nd.


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