Warmer than Average Winter Expected
El Nino is in full swing across the Equatorial Pacific possibly reaching record levels! For us that could translate into a warmer than average winter across southern Wisconsin.
During an El Nino, the polar jet stream (a river of air) is shifted northward, which limits cold air intrusions from the north. This pattern brings above average temperatures to much of the northern United States, including southern Wisconsin, and below average temperatures to parts of the southern United States.
The Pacific jet stream is across the southern United States. This helps to bring moisture to parts of the southern United States. El Nino is also associated with below average precipitation over the east-central United States.
The tough part about this El Nino is there are only about 6 analog years since 1950 to compare it to. Take a look at the picture in this blog. That's the temperature forecast from the Climate Prediction Center.
The winter was very warm during the very strong 1997-98 El Nino. Temperatures were 6-8 degrees above average. Precipitation was up to 2 inches above average; moreover, snowfall was up to 10 inches below average.
In general very strong El Nino's produce lower than average snowfall across southern Wisconsin.