November got off to a quick start in terms of winter weather this year. The first half of November was heavily loaded with below average temperatures and a widespread, accumulating snow event. Just as quick to follow was a thaw to close the month out.
You may remember our report back in October where we gave you a taste of what the climate prediction center had to say about the upcoming winter season. The CPC released their latest for winter in late-November. In general, not much has changed-- perhaps a stronger signal to colder than normal air, and a wetter pattern for mid-Missouri.
What has been a big driver for that forecast, and the one you saw featured in Chief Meteorologist Jessica Quick's long range forecast is the Arctic Oscillation.
The Arctic Oscillation is a value measured by meteorologists to assess wind patterns in the top of the atmosphere. When the value of the A.O. is positive, the weather tends to slow down-- much like this week.
However, when the value of the A.O. is negative, the jet stream tends to become wavier, leading to mild weather over the central Pacific Ocean, and cooler air across the central United States.
Some proof of this idea can be applied to what we saw in November. For much of the beginning of the month, Arctic Oscillation values were generally negative, leading to the cold and snow. Near the end of the month, into the first few days of December the A.O. has been largely positive, leading to our recent thaw.
Another shot of cold air is expected next week, as A.O. values are expected to drop.
This seems like it will end up being the trend for most of the winter, so strap in! Many more ups and downs are ahead.