Glenn Zimmerman’s long-range St. Louis winter weather outlook

Weather

ST. LOUIS, Mo. – Let’s take a look at the forecast for this upcoming winter. I’ll start with our standard disclaimer: Long-range weather forecasting is an inexact science. There is no data or information that can give us specific storm timelines. But, what we can do is give you a general picture of each month using long-range data and trends. With that, let’s dive into winter!

There are so many sources for weather data these days. Long-range models show trends in precipitation and temperatures. Global forecasts show the position of the polar vortex throughout the year. We pay attention to that in the winter especially.

Over the past few decades, we have been tracking sea surface temperatures. They play a huge role in changing the steering currents in the air, called the jet stream, and how that river of air moves in different ways. The sea surface temperatures in the Pacific this year point to another La Nina winter on the way. It’s the same scenario that we had last year.

So, there are two La Nina winters in a row. Has that ever happened before? The short answer is, yes. When we plug that and other information into our computers we find many similar years. We will use last winter as our guide.

December:

There is strong research being done that relates a cold month of May, an active hurricane season, to the severity of winter cold. We’ve already seen a couple of fast pattern flips this month so the pattern is already starting to show its cards: December looks cold. Below normal cold. In fact, the coldest month of the winter very well may be December. We haven’t seen that happen often. We would normally say that January is the coldest winter month. But this year, there’s a switch and the period between Thanksgiving and News Years’ Day will average out to be the coldest.

Cold air means dry air which means that there are not a lot of chances for precipitation. That brings us to Christmas: There are three ways to look at the possibilities of a white Christmas.

First: we haven’t had a white Christmas since 2017, so if you play that percentage, we are due.
Second: After 100+ years of climate data for St. Louis, there is only a 20% chance of a white Christmas, that’s pretty low.
Third: last year, a La Nina year, we only had 1/3 of an inch of snow all December. If this year is the same pattern, then the percentage is low.

I am going to go with the pattern and the percentages and say that there will be no white Christmas this year again. Now, if a rogue storm forms a few days ahead of the holiday, then all bets are off. Overall, this December is colder than last December. The chill is on. And just like December 2020, December of 2021 will be mostly dry. Not a lot of snow.

January:

January will start with the remnants of the December chill. At least the first part of the month will be below normal. But, the later stages of the month will flip back to warmer than normal. We like to call that the January thaw as if it happens every year. But I think this year it will be a noticeable flip. Those kinds of transitions in the pattern always bring precipitation, and in January that usually means snow.

Last January we only had three inches of snow all month and most of that came in one late-month storm. I think this year there may be more than that.

As for temperatures, last winter’s January was warmer than normal, and this coming January will be closer to that too but several early month days the highs won’t get above freezing.

February:

I say this every year on this winter special: February is the shortest month, but it’s the longest month. It’s normally cloudy and cold and you’re waiting for spring the get sprung. I think we have a weird February coming.

Initially, some of the January “warmth” will carry over to February only to transition back to cold. That transition may come in stages with each stage bringing precipitation. So, if you get my drift, it could be a snowy month.

Last winter we had a really cold February. This year I don’t think we will be as cold, but cold enough. Last year we had almost 9 inches of snow in February with most of that coming in the middle of the month. This coming February we could see just as much snow but will come in several smaller storms.

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