When looking at what to expect this winter there are a few things to consider.
The first is whether we are in an El Nino, La Nina, or a neutral year. These are terms that reflect the strength of the trade winds and the temperature of the water in the equatorial Pacific. The reason we care about that is it has major impacts on the upcoming weather all across the globe, including here in the Tennessee Valley.
This year, like last year, we are in a La Nina year which means the water in the equatorial Pacific is colder than normal. That pattern typically means the jet stream, or the strong river of air in the upper levels of the atmosphere, runs further north than usual.
One way to look at the jet stream is as the dividing line between colder air to the north and warmer air to the south. When the jet stream is further north, that allows warmer air to lift further northward and typically means a warmer winter for us.
The pattern of the jet stream during a La Nina year can also impact the overall precipitation. The jet stream further north keeps the track of any weather systems further north also as they are steered by the jet stream. So typically during a La Nina year like this one, we are drier than usual as well.
In looking at long-range model data there is fairly good agreement among the models that our temperatures in December, January, and February will be warmer than normal. However, the seasonal forecast models stray away from the "dry" leaning of a typical La Nina year. As a matter of fact some data shows a fairly wet winter.
With all of that said, here is my outlook for this winter.
TEMPERATURE - Above normal temperatures with the average temperature for the winter being about 2º to 4º above average.
RAINFALL - We are going with the model data on this one. Even though La Nina typically calls for a drier year, there is enough evidence to suggest we will have at least a normal rainfall year if not a little above normal. On average we get about 15" Dec.-Jan. I am calling for 15"-18" of rainfall this winter.
SNOWFALL - You have probably already guessed, but with the overall warmer-than-normal outlook that would indicate below-average snowfall as well. In the valleys we can expect a trace up to 2". In the mountains we would expect a little more. I would anticipate 2"-4".