Champaign-Urbana came out of the weekend with a final tally of 3.8" snow accumulation from the storm over the weekend - well shy of the 6-8" that I had been forecasting for much of the day on Saturday. What happened?
Snow forecasting has given meteorlogists a real headache this winter - and no one has been more frustrated than myself. I was nearly ready to toss my weather maps into the air and throw in the towel on Saturday night. There was a big conflict on the actual track of the surface low pressure center, which was the main player in where the highest snow totals would land.
North of the surface low track - colder temperatures would allow for almost 100% of the precipitation to fall in the form of accumulating snow. Along and to the south of the track, warmer air being drawn up from the south would keep temperatures above, or right at freezing allowing rain to mix in and dramatically cut down on snow accumulation. It's pretty simple - any precipitation that falls as rain, won't be accumulating on the ground as snow.
What isn't simple, is trying to nail down the exact track of that rain/snow line. I was very clear on us seeing quite a bit of rain early on in the event on Saturday night. What I was not expecting, was the surface low to track *north* of us, which aside from a brief period on Sunday morning where we saw all snow, kept us in a rain/snow mix, and even at times during Sunday evening - all rain!
The National Weather Service provided the map below that shows snow accumulations across the state of Illinois from the weekend. I have overlaid the forecast track of the surface low from Saturday morning on one map, and the actual track on Sunday on the other. The difference of approximately 100 miles between the forecast track and the actual path the surface low took made all the difference. Rather than seeing rain on Saturday night before permanently switching over to a prolonged period of accumulating snow during the entire day on Sunday that would have easily put CU into the 6-8" range - we saw a brief period of snow which allowed 3-4" to quickly stack up before warmer temperatures being ushered in ahead of the surface low warmed us back to above-freezing temperatures and switched us back to rain.
There is a saying in meteorology - if you can't forecast well, forecast often. And my biggest downfall may just be my propensity to go down with a bad forecast, much like a sea captain going down with his ship. I spent the afternoon on Sunday splitting degrees, waiting, hoping for us to make that fraction of a degree drop that would switch us back to snow and it just didn't happen. I apologize to those children who may have been hoping for snow days on Monday!