Warm Layer Aloft Turns Snow to Sleet in Louisville (Full Transcript)

[00:00:00] Speaker 1: The dreams of a record-shattering historic snowfall in Louisville, Kentucky, where I'm located, likely shattered. Here's the reason why. Take a close examination of the type of snow that fell overnight. See those little granular ice pellets? That's known as sleet, and it's all determined by the temperature that's directly above us. So I've got this demonstration. The blue panels here representing the temperature that is below freezing in the atmosphere. So if it was to be all snow, the precipitation that falls through this would stay frozen. But if we get what's known as a warm nose of temperature that's above freezing, it allows that precipitation to actually melt right here before refreezing at the surface, creating the ice pellets and also limiting the amount of snow that falls from the sky. What we do not want to see is when that warm nose becomes so thick that there is only the shallow layer of temperature right above us. Right at the surface below freezing, this is the situation when precipitation falls as freezing rain, because it melts into liquid and then refreezes at the surface, and that's when we have crippling ice storms.