Louisiana = Minnesota…. Apparently

February 22, 2010

What’s the deal with this winter?  We’ve had two measurable snows, one day with off and on snow showers, and we’re staring at another potential snow for late Tuesday/Tuesday night.  I will say this from the get go.  With the December storm, I was 90-95% certain we’d see snow 24 hours out.  With the February storm, I was 75-80% we’d see snow 24 hours out.  With this “storm”, I am 40-50% confident we will see snow, and we are 24-30 hours from the onset of precipitation. 

The main difference with this storm is marginal temperatures in the low levels.  Instead of being 31-34 degrees with cold upper levels, we will be around 42-45 at the onset of precipitation, and will fall into the 34-37 degree range as precipitation falls.  We will saturate, and cool from the top down.  That means snow will be generated aloft.  As it falls through a sub-freezing layer, it will stay snow until about 2000-3000 feet up.  At that point we slowly rise above freezing.  Without getting too technical, this “top down cooling” effect will cool the lowest layers of the atmosphere.  We are basically introducing ice crystals at lower and lower levels in the atmosphere.  As precipitation rates increase, snowflakes will get together aloft, and fall at a faster rate.  If rates are high enough, that will force the snow levels down in the atmosphere.  If we were sitting at 2000 feet above ground level tomorrow, I’d be forecast 1-4 inches of snow.  Since we aren’t atop the Sears Tower, I will be much more conservative.  Right now, I’d say around an inch is possible in patches around the area.  However, Sabine, Natchitoches, and Winn parish stand a chance to see 1-3 inches of snow.  This could change slightly with the evening model runs.  I’ll post then when I have more time.  This would be big news any other year, but at this point I think this will be our 3rd biggest snow storm of the year……..  in Louisiana…… crazy.

Nick

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