Cold pattern ahead, but no major storms…til March?

In my last post I described the typical scenario for how the Mid-South can receive accumulating snowfall from an Alberta Clipper. And wouldn’t you know, the current radar shows a clipper streaming in from the NW headed directly for the Bluegrass region.

Since clipper storms have a very sharp snowfall gradient south of the storm, there is little hope for accumulating snowfall in south-central KY, which is still technically snowless for the winter of 2007-08 (snowfall data was not collected last Wednesday at the Bowling Green airport and the snowfall is listed as “missing” even though I would bet at least 0.1″ of snow fell that day). Southern IN and northern KY should get an inch or two as the clipper skirts by overnight.

The next storm for Thursday/Friday is very similar to the storm last week that brought snow and sleet to northern KY. The overall synoptic pattern shows a split flow with an active but zonal southern jet stream along with a meridional polar jet. The NAM shows an area of wintry precipitation along a warm front extending eastward from Missouri into southern IN and northern KY Thursday afternoon (again, nothing wintry for southern KY). As the surface low deepens to the west, southerly flow will force the wintry precipitation northward and things should be all rain by Friday morning.

Looking at the long range, the pattern remains split with an active but zonal southern stream which means numerous but weak storm systems that are primarily rain for the Mid-South. What is interesting to me is that beyond 10 days, the polar vortex appears to sink southward and become trapped beneath a fast zonal jet stream. Since arctic air north of a zonal jet is dynamically unstable, there should be a transition to a meridional and potentially stormy pattern with an active jet stream during the first half of March. This type of pattern could continue the record breaking tornado season for 2008.

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