Needless to say, as I sat stuck in nearly 4 inches of heavy wet snow on a nearly closed I-75 near the airport, my first thought was "How did we arrive at this?" The area was STILL not under a winter storm warning, and no one had forecast anywhere near that much snow this far south. In fact, KCHA managed to very quickly accumulate more snow in 4-5 hours than many places farther to the north saw during the entire event. And then came the ice. Most residents of Lookout Mountain still don't have power as I write this. Fortunately, the icing was not significant enough in the valley to be much more than a nuisance.
In the hours and days leading up to this event, no model (not even the allmighty EURO) had 850mb temps in tandem with 2M temps that would support snow. Some were close, but usually provided a sounding of brief IP/ZR towards the end of the event.
The storm, it seems, actually played out in reverse. Temps were hovering near freezing with dewpoints near 20 degrees. As the precipitation began, we wetbulbed down to 31 degrees and stayed there for most of Friday. The snow started as some flurries, but then quickly turned into the heaviest snow I have ever seen. I went to Publix for 30 minutes, when I got back to my car there was nearly 2 inches of snow on it. Unbelievable rates. Every once in a while, there would be an abrupt change to 100% sleet, but then it would change straight back to 100% snow. There was rarely any mixing, it was usually one or the other. That snow piled up FAST when it was falling. I feel that if we had not had periods of sleet, we would have easily cracked the 8 inch barrier before changing to ZR.
So why were the models so terrible at predicting temps in the snow growth region? They were just about as wrong as they could have been, and they have left our local MET's scrambling to find an explanation to their unhappy viewers. Even the normally conservative MRX was completely thrown for a loop. When they finally saw fit to issue a winter storm warning (after Chattanooga had amassed more snow than any other area in the CWA) they hastily upped the forecast totals to nearly 9 inches. Of course, almost immediately after they did this, the warm nose finally won out and we changed over to ZR, then to 33 and rain (our original forecast).
So my point is this: clearly this was a pretty bad miss on the part of the models and our METs, but what specifically happened during this event that caused us to stay all snow for so long when no one thought we could? I am thrilled that it played out the way it did, everyone here knows how overdue we were down here, I am just trying to understand where the models and forecasters went wrong here, as everybody in the area was caught off guard.
