Well, as I talk about in the text portion of the forecast, confidence has increased from yesterday's forecast and I think there is probably a 70-75% of a strong low pressure to impact the upper Midwest. The larger questions are the exact track (which impacts where the snow falls) and to some degree the exact amount of snow it would produce.
In general, when I use solid shading on the maps, I believe there is at least a 50-60% chance of it happening and many times in the maps for the next 3 days the percentage is as high as 80%. When I use a line and put text inside the line, then I think the chances are less than 50%. So for this system I am at about a 55-60% chance of things happening as currently indicated and about a 70% chance of someone in the upper Midwest to see a big storm.