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Snow, Rain, or Wintry Mix - Wednesday

Snow, Rain, or Wintry Mix - Wednesday

by Monty Webb

WHAS11.com

Posted on February 12, 2013 at 12:02 AM

Updated Thursday, Dec 5 at 2:22 AM

Rain, Snow, or Wintry Mix - Wednesday's forecast is shaping up to be very challenging!

When we forecast winter precipitation, meteorologist look at many different elements to determine whether we will see frozen, liquid, or a mix precipitation.

First, is there available moisture... and the answer for Wednesday is YES.  The GFS model tracks a low to our south and we can see the moisture/precip in green on the thickness map below.  Something that is interesting to note is the 540 line (snow-line) is also to our south.  Generally you want the 540 line south to see snow in Louisville, but hold on snow lovers it's not that simple.  Other factors are in play!

The second item we analyze is the upper air sounding (SKEW-T).  It is a vertical cross-section of the atmosphere that will show us the temperature profile from the surface to over eight miles above the ground.  For frozen precipitation we are concern more about temperatures near the surface.  Take a look at the Skew-T forecast sounding for Wednesday morning.  Notice there is a shallow layer of warm air ABOVE freezing near the surface and  then the temperatures fall rapidly BELOW freezing.  With this type of temperature profile I would expect rain and/or a rain/snow mix.

However, if we see any heavier showers on Wednesday it could pull down the colder air and give us a quick wet snow accumulation.  But, with the road and air temperatures above freezing it would quickly melt after the shower ended.

Weather Models Have Different Solutions...

The models have been all over the place the last couple of days and changing accumulation amounts run to run.  Take a look for yourself...

The NAM paints out a trace for the Metro with heavier amounts to our south and east. (I think the NAM is WAY over doing snowfall amounts)

The GFS is more realistic showing just a trace, but with the ground and surface air temps above freezing even a trace accumulation might be difficult unless we see a heavy shower.

My favorite model for Wednesday is our own Futurecast, which is not showing any accumulation.  Stay tuned and we'll keep an eye on Wednesday for you!

 

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