The clipper that will move through the Mid-South early this weekend will not be a big snow producer for south-central KY, although taken at face value, some of the model outputs suggest that it could.
Using Wedneday’s 12z run, one can see that prior to the clipper diving south out of Canada, there is a cold cP air mass in place Friday evening with thickness lines and 850 temps favorable for snow. However, recent models runs have trended north with the clipper, and by Saturday morning, the vort max associated with the clipper is located over southern WI. This means that south of the vort max, WAA will take place enough to raise our 850 temps to just above zero, which means precipitation will probably start as rain, even though the 1000-500 mb thickness is still below 540 dm. This can be more clearly seen with the SREF models on the SPC website. Just click on the most recent model run and look at the “Winter weather” tab for information on P-type and snowfall accumulations.
A good rule of thumb for clippers is that the heaviest snow will fall along a 100-mile wide band north of the 500 mb vorticity axis. There is typically a sharp snowfall gradient to the south of the band and a more graduate snowfall gradient to the north of the band.
Here in BG, there will be a transition over to all snow once the cold cP air is reinforced behind the front, but anything more than a coating is not expected at this time.
