This is a perfect time and place to talk about the difficulties in forecasting snow. It is probably the hardest part of forecasting for us. Rarely, winter storms are predictable well in advance. A small change in the storm track can have huge implications on a forecast.
Let’s take tonight’s example. At this point, it looks like a weak area of low pressure will move right over southern Wisconsin later tonight. There are still many variables to change the forecast at the last minute. Here are the questions that I am asking myself right now as I wait for the next computer model run to come in. We use many different computer models when forecasting and look for consistency from one model run to the next. I am worried about the fairly warm temperatures that the precipitation will be moving into later tonight. However, we still have pretty low dew point temperatures that will allow evaporative cooling to occur and likely quickly change any rain over to snow. However, the dry air can also take some of the moisture out of the air. Furthermore, the low is expected to intensify a little as it approaches. If it does not, we will have little if any snow.
At this point, 7:37 PM on Sunday evening, I am forecasting a rain/snow mix to move in around 2AM and change over to snow pretty quickly. It does not look very heavy, but it is coming in at a bad time with the morning rush likely to be pretty slippery. Stay tuned.