Nowcast Mode - One Last Look at the NAM

The 18z run of the NAM is as far as I'll take these types of models. I will be switching to nowcast mode after this post. In addition to current observations and radar trends, the Rapid Refresh short-term model will be my model of choice. Quite literally, it will produce an hour by hour look at things like precipitation type, accumulated snowfall in 1-hour increments, preferably, and 850mb temperatures.

First, look at the 18z run of the NAM. Funny thing. If you look at the total snowfall map, you would think omg, it's Snowmageddon. However, I feel quite certain that Bowling Green will not get over a foot of snow from this system.

Why? One look at the 850mb temperature profile shows that when it appears Bowling Green is getting slammed with white-out conditions, the temperatures at this level are forecast to be too warm for snow. However, freezing rain and sleet will be the main precipitation types for the first two 3-hour periods. Snow will finally mix in just before and during the last 3-hour period of their Snowmageddon. Therefore, their 12" snowfall will probably only amount to 3" snow if that. However, I would be more concerned about ice and sleet accumulation for them.

In Lexington, what looks like at least 4" will probably only amount to nearly half that, 2 - 2.4". Again, ice accumulations could become a problem, but not as bad as downstate.

Louisville could be looking at 1-3" snow. Ice accumulations of at least 0.2" with some sleet accumulations of up to 0.5" as well.

This is what I consider to be the most accurate part of the NAM.

However, these types of systems are always hard to forecast. This same model wants to show a heavy band of snow developing somewhere in central KY. Where that sets up, someone is going to get at least a half-foot of snow with ice accumulation underneath.

Nowcast mode next....

MS