Patrick Powell's 2017-18 winter forecast
(WLUK) -- Will you be golfing this December like many Wisconsinites were in 2015?
Or will you be digging out your mailbox so you can get to your Christmas cards like in 2008?
For the last 13 years, I have been making a forecast for the winter here in Wisconsin. While it will obviously have snow, and will inevitably have cold snaps, I try to compare what I am expecting to an average winter to help you prepare for the months ahead.
Seasonal forecasting is a much more general prediction than the detailed weather prediction we do for the next day. Seasonal forecasts are based on atmospheric patterns which drive the jet stream and lead to the overall weather for the winter.
I look at three of the main influences of the winter climate for Wisconsin to make a forecast:
- I research the early-season snowpack over Asia and over North America. This is a newer area of study, but a high early snowpack leads to more cold shots and more snow.
- El Niño or La Niña are major factors for seasonal forecasts. There are the ocean temperatures in the tropical Pacific. La Niña winters are colder and produce more snow.
- Also, we take the Pacific Decadal Oscillation into account. Temperatures tend to be similar here in both phases, but the warm phase produces about 10 inches more snow for our area.
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For this year, the snowpack over North America is at record levels, while Asia is at the second-highest level on record. I am expecting a weak La Niña for the winter, and the PDO is near neutral.
While a high early snowpack, especially over North America, leads to temperatures that are about 7 degrees colder on average over the winter.
The average difference for us between an El Niño and a La Niña is about 20 inches of snow, with La Niña winters being some of our snowiest.
I am forecasting temperatures slightly above average for December, average for January and February, then below average in March. I think the winter will be slightly below average overall with some sharp cold snaps.
Snowfall-wise, I am expecting slightly above-average snow in December, average snow in January, then more snow again toward the end of winter in February and March. I do think snowfall will be above normal for the season with 55-70 inches for Green Bay.
For the winter, I am looking for slightly below-average temperatures. My forecast total snowfall of 55-70 inches is above average. I think we will have 4-6 named storms and the snow will be loaded to the early and later portions of winter with a lull in the snow during the coldest portion.
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