Wednesday afternoon. 1/20/2016

Pretty, light and fluffy snow overnight and this morning left a coating of 3″ on my driveway and 4″ at the airport.  Similar totals around most of the area.  We’ve been talking about the main event this week being Friday’s expected storm, but today’s snow has raised the bar a bit.

There have been some interesting changes in the models since yesterday’s runs.  The most prominent one is that both the GFS and the NAM have dropped the system farther south.  Yesterday, they had the axis of heaviest snowfall right over the Ohio Valley while today they have the Ohio River just inside the northern edge of the snowfall shield.  There’s likely to be a sharp drop off in snow along the northern extreme of the precipitation area, so that’s a very important development.  Another interesting result from the morning’s runs is that, even though they’ve made the southern shift, the models haven’t changed their snow forecasts for us – generally 6″ – 10″.

To me,  that’s a very surprising development, one that doesn’t make a lot of sense.  There’s another problem – the storm diving over the Rockies is expected to eventually “cut off” from the main band of westerlies and drift slowly eastward and then get re-absorbed into the upper flow and become a huge east coast storm for the middle Atlantic states.  The time while it drifts over the southern states will be when it will have it’s greatest effects on us.  That drift was expected to be very slow, putting us in its path for a longer time.  The GFS is still predicting that, but the morning NAM ejects the system much quicker eastward, thus diminishing the duration of snow.

There’s no question that this storm will be able to tap into a vast supply of Gulf Moisture.  But, it seems the biggest question for us is “How far north will the moisture come?”

So, it’s obvious the Friday’s weather is still “up in the air” so to speak.  Tonight’s and tomorrow’s model runs should go a long way toward resolving the situation.  Until then, here’s my current thinking…I believe the shift to a more southerly storm track will, in general, hold.  I believe that the  GFS and NAM will come to a compromise over the evolution of the cut off low’s ejection eastward.  If it works that way, the axis of heaviest snowfall will be over southern KY/northern TN and go ENE from there.  thus the heaviest snows should fall from Nashville and Bowling Green to southeastern KY, West Virginia, northern MD, southern PA and New Jersey.  The western half of that area could see snows in the range of 6″-12″ while the eastern half could reach 12″-20″ or more.  That puts us on the northern side of the heavy snow axis, an area which should see rapidly diminishing snow totals northward from Bowling Green.  For the Louisville area, my current outlook would be in the 3″-6″ range (higher south and east, lower north and west).

That’s it for now.  I’ll be back tomorrow…probably with a completely different story.