Monday Mid-morning

An EARLY glance at the 12z NAM suggests total QPF from this system in the .50 to .75" range for a large swath of our region. Thermal profiles off the latest run suggest mainly snow from near Louisville and points north - with a snow to rain then back to snow scenario for areas south of Louisville.
NAM 21hr fcst sounding for SDF (valid 15z Tue) did have a small layer near 950 slightly above critical. It's certainly possible there could be a brief changeover to rain or a mix for a few hours tomorrow mid/late morning in Louisville ... but I would think this would have a better chance of staying all snow in Louisville due to the fact that the upper system is still dropping south of east somewhat and this tends to lock down (or at least slow down) the movement of the thermal patterns not to mention that although some warming of the column is likely - much of the WAA (warm air advection) is likely going into vertical motion and precip generation. As a result, the column may stay colder (and all snow) than what the new 12 NAM is suggesting. And even if we did see a brief changeover (I'm talking about the Louisville metro area here), as I mentioned above it would likely be brief and on the tail end of the widespread precip shield. Bottomline, overall snow amounts would likely not be impacted all that much even if there were to be a brief changeover.

QPF amounts off the NAM are definitely higher... we'll see what the GFS has to say about both the QPF and thermal patterns. But if the GFS comes in agreement with the NAM, it's very possible we'll be upping the amounts some again before tonight's 5 pm newscast.

Also, I can't stress enough how wintry snowy, windy, and cold) it's going to be around here tomorrow night into Wednesday morning. Although the heaviest of the snow will be over, as the upper low shifts through the region, periods of light snow, flurries, and snow showers will continue. Additional accumulations with this activity will be light and generally lesss than 1 inch but the winds will be gusty with some blowing snow and the temperatures down as wind chill values could be approaching 0 degrees overnight Tuesday into Wednesday morning...

We'll have another "official" expected snowfall update later on today

Jay