Technical forecast discussion from @NWSNashville just posted, describing several factors that could reduce or supplement 0.5" to 1" expected tomorrow. I hereby attempt to unpack it. A thread 1/
2/ Some models think surface temps will drop only into the mid 30s, then stop there. Splat/Melt would "dramatically cut snow totals."
3/ However, other data shows dry air aloft that, once the Dry Air Monster (D.A.M.) is fed, will lower surface temps ~ freezing. When the D.A.M. eats, the air around him cools. This is called "evaporative cooling," or if you're a cool scientist, "wet bulbing" to freezing.
4/ Or, the D.A.M. could be really hungry, evaporating all the snow before it can reach the surface. Maybe he leaves us a few crumbs. nashvillesevereweather.com/product/dam-sh…
5/ Another uncertainty is the speed at which we get to freezing -- any delay will limit accumulation even though sleet and snow is falling. The margins are razor thin.
6/ If snowfall is a brilliantly played rendition of Beethoven's 5th, then we're a day away from the performance, we've hired musicians, but we don't know if those musicians will all show up, are familiar with each other, will bring their instruments, or can play well together.
7/7 After all that, the consensus/middle ground is 0.5" to 1" for us. Bridges, overpasses, elevated areas are more exposed to travel impacts than primary and secondary roads. We'll just have to see which musicians file in the performance hall tomorrow.
