The Thursday version of the EURO EPS weeklies are in and what a run this was for early season snow in the Midwest. I'll show you the snowfall output over 46 days and then discuss the pros and cons of it actually happening. First the amounts on the control.

Now the ensemble mean.

What are the chances of this happening. Let's start with the negatives. First and foremost, any forecast that goes out 46 days has plenty of room for failure. The farther out you go, the less likely the chances of verification. The prediction also relies on correct placement of the storm track. That means the model needs to nail the southern extension of the cold air necessary for snow production. Last but not least, the model must accurately determine the size and intensity of disturbances that have the potential to create accumulating snow. These are all big challenges.

So how do the forecasts come about. The idea of the EPS is to account for uncertainty in the initial weather conditions by creating a set of 50 forecasts starting from slightly different conditions that are close, but not identical, to our best estimate of the initial state of the atmosphere (the end result is the control run). The (mean run) is similar but with small changes made to the initial conditions. It's far more smoothed and more of an average. Usually a more reliable indicator. Anyway, you can see how the two forecasts come about.

The positives with regards to potential snow is that the model is showing it widespread and in large amounts. Sometimes you see a little swath 150 miles wide. In this case there's lots of territory involved and the amounts are significant. This represents a trend. The exact location and amounts will never verify as shown, but the odds are pretty good that some parts of the Midwest will see decent snows by late November or early December. More than what's typical.

Unfortunately, we wont be able to see the results of the EPS forecasts for 46 days ending December 9th. All I can say to you snow lovers is, "wouldn't this be nice". Roll weather...TS

© 2020 Terry Swails