OMAHA, Neb. (WOWT) – The atmosphere and ocean waters are definitely showing changes as we approach the coming winter. These changes presented quite a challenge as I established my winter outlook this season. There were, however, some things that stood out that might help tell the story for us this year. Let’s go.

First of all, we are definitely moving from an El Niño to a La Niña as we approach the winter months. Colder than average ocean waters are appearing along the equator in the Pacific Ocean, but the biggest question is how cold they will be and how strong La Niña will be this time around.

Today, no two La Nina winters are exactly the same, but they tend to lead to a certain jet stream pattern that influences our weather to some extent.

Overall, a northwesterly flow pattern will likely prevail for most of the winter. This means that most of the time, the upper-level winds that drive storm systems blow northwest to southeast across our region. Sometimes there will be shallow or deeper troughs (troughs) in these jet stream winds, which can lead to chances of snow and rounds of cold air.

Another factor I look at is called the Pacific Decadal Oscillation PDO). This is a longer-term climate pattern that affects the temperature of the Pacific Ocean and the weather patterns around it. This has been negative for a long time and could be part of the reason why we have largely been dealing with a drought over the last 4-5 years.

If you look at all the times since 1990 that we have been in a La Nina for the winter season combined with a negative AOP, there tends to be certain trends that stand out.

On average, this leads to a warmer than average winter season for us across much of the country with cooler conditions in the Pacific West and Northwest.

There are also notable trends in precipitation. Note a drier than average pocket near our area and a fairly well defined, wetter than average path from KC through the Ohio Valley.

I’m also looking for patterns over 2-3 years where we alternate between El Nino and La Nina. In this case, with the forecast of a La Nina for the following winter, we are looking for a La Nina, El Nino, La Nina pattern over a 3 year period. I used it and looked at past winters to find similar models. There were about 4 winters that really stood out to me and a 5th that is definitely worth watching.

1973-74

1998-99

2007-08

2010-11

All of these winters resulted in below-average humidity, but a few of them managed to turn that humidity into slightly above-average snowfall. These 2 maps show the combined precipitation and temperature trends for these 4 years.

There was a fifth winter that I don’t want to completely ignore, 1964-65. That winter was crazy with the humidity and snow and we ended up with a little over 56 inches of snow. This La Nina was weak and even weaker than I think we will see this year. I’m expecting at least a moderate La Nina, so I’ll stick with what these other 4 winters have told us so far. However, I will NOT ignore what happened this winter and we will watch for signs that we might be in for a winter treat.

On that note, I expect January to be the big month. Most longer range models suggest this will be the coldest winter month. That’s pretty typical. The key will be how much snow we can develop that month. More snow cover likely means a colder end to the season and vice versa. Right now I think with the expected pattern and where I see the main axis of heavy snow setting in, I’m leaning towards a drier than average winter with temperatures slightly above average for our region. Overall, I think most cold snaps will be short-lived, with west downslope winds from the Rockies helping to warm us up quickly as the cold air escapes. A few larger blasts might favor our best snow chances, but we’ll probably wait until mid-winter for them to try to get us. Most of the colder air and snow passes to our north or only fully develops when it is east of us, over the Great Lakes.

The average snowfall in our area is about 28 to 30 inches, so I think a range of 22 to 28 inches for the season seems good, but keep in mind the wild winter I mentioned . We will likely stay below average, but we could go A LOT above average if La Nina is weaker than expected.

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