We have been seeing extreme model flip flops back and forth for the last several days, It seems to me that ever since the models did their upgrades, the volatility from model run to model run has increased considerably. Add to this a strong negative North Atlantic Oscillation and a lot of turmoil in the stratosphere, and you have the ingredients for a lot of forecast flip flops. It is important in situations like this to gain a grasp of what is happening in the atmosphere and why it is happening. Right now there is a lot going on.
The NAM model for Sunday evening illustrates very well what is happening. We have 3 distinct short waves in play. The first in the Great Lakes is most definable on the European and Nam models and almost non existent on the GFS and Canadian weather models. If this is an intact system then we could see a period of light precipitation Sunday night into Monday morning in the form of either light rain or some wet snow. As of right now the European model is delayed due to a power outage. After that it is the system in the southwest that weather models have been having huge difficulty with and how that system interacts (if at all) with the third short wave in the Northwest. Earlier this week weather models were basically phasing this system and creating a huge blizzard for the upper midwest..read more at http://www.meteorologistjoecioffi.com/index.php/2016/12/01/weather-models-bi-polar-behavior/