Happy Thanksgiving! Our Winter Weather Special will be on Saturday December 4th at 11 AM. We’ll show you our forecasts from last year…and we’ll give our thoughts about this upcoming winter. Usually though I like to get a bit ahead of that though with the blog…and while I have some rough ideas on a range of snow that I will be forecasting this winter…I haven’t clarified the direction I want to go in. That will be handled on the special on the 4th. IF you miss that, I’ll be going over the predictions during the newscasts on that Monday the 6th. So put a note on your phone/calendar about all of that!
Winter forecasts are funny things…at FOX 4 we try to pinpoint a specific accumulation of snow for an entire season…some seasons the snow stops in February…other seasons it stops sometimes in April. Heck about 15 years ago it stopped in May! One number…one place. KCI. That too is bizarre…because as we all know snow forecasting here varies from north to south…sometimes to excess. We’ve seen 4-8″ ranges just across the Metro before and within the viewing area…25″ seasonal ranges aren’t surprising to me.
We approach this forecast individually. We all have our opinions BUT then we average all the forecasts together and that is our “team forecast.” We also forecast the coldest low temperature (again individually) and then as a team average. So it’s a two tiered approach.
Just the fact that individual snows typically have some variation to accumulating numbers around the area…then trying to take that all into account to come up with a seasonal average is a bit on the cray cray side but it is what it is and during this time of the year it’s the most common question many of us get.
As you know I like to take some deep dives into my ideas…sometimes with success and sometimes without. All in all though…this can be fun enterprise and yes…within the weather team we do enjoy seeing how close we get or don’t!
So with all that said…onto some thoughts about this winter.
The elephant in the room is that this once again is another La Nina winter. La Nina is a cooling of the equatorial Pacific waters. It varies in strength…sometimes strong…sometimes weak. This La Nina is teetering at times into “moderate” conditions. There is a specific area that we look for for La Nina. It’s towards the equator between South America and Indonesia
You can see the temperature anomalies more clearly…looking at a more global view.
There are other things to pay attention to as well including the warm anomalies in the Atlantic and the Pacific towards the NW of the Hawaiian chain of Islands. Also there is some cooler water compared to average in the NE Pacific Ocean
Sometimes La Ninas fade…but this one has had staying power…and when looking at the depth of the cooler than average waters…they’re substantial. Meaning this La Nina isn’t going anywhere for awhile. Notice on the far left side the numbers going from 50 to 200. That is the depth of the waters…and the blue contouring represents the anomalies as you go down through the waters.
Why is all this important…La Ninas do tend to play around with the “average” jet stream location. Notice I used the word average…really it’s more of a tendency. La Ninas in and of themselves help to create a variety of weather in the northern hemisphere…BUT, and this is important…they are not the end all be all of all winters. There is so much variation and some many other things that can influence the jet stream positioning on a week to week basis…that it’s JUST NOT all La Nina. Some of the processes we understand…others we don’t.
The typical tendency though of La Nina winters is sort of this idea.
and it’s no surprise that this is roughly what the NOAA forecast is showing for the upcoming winter.
Last year was a La Nina year as well…and these were the forecasts issued. A lot of similarities right?
So what happened last year? Temperature anomalies…
The Northern Plains was a terrible bust on multiple accounts.
Again I don’t like to put ALL my eggs into the La Nina basket.
There are other things…including what’s happening in the Pacific…tendencies that have been happening in the fall etc.
Speaking of which…how have things been going this fall. Well since October 1st through yesterday…
So overall warm and wet although the latter situation is really changing these last few weeks and there doesn’t appear to be much moisture coming for awhile.
Will this persist?
Last winter was a warm winter BUT we had the 2 week period of extreme cold in February and that changed everything. We were running 5.1° above average in December…5.3° above average in January…and then February saw the flip. That 2 week stretch from the 5th or so through the 20th or so sent the average February temperature down to 10.3° below average wiping away most of the warmth from the previous 2 months. An incredible switch really. Heck even March was 6° above average.
I lean towards a milder winter overall in the end for 2021-22. That two week stretch of cold to that extreme I doubt will be repeated in the region.
Also of note for the way things have been going these last 7 weeks is a pronounced lack of snow cover in the States. This isn’t crazy unusual BUT there is also a real lack of persistent cold air anywhere really. In the last 2 months…this has been the trend and while the data below isn’t perfect…it sort of gets me where I’m going.
Alaska has trended cold though…that can be a double signal for the States…typically when they’re cold we’re milder and also when they’re cold…we can also get some cold pushes when that air sloshes over into the western reaches of Canada…it can be tapped to move southeastwards given the right jet stream switch (which I do think will happen on occasion…with pretty drastic results compared to the overall above average tendency).
Another thing I noticed…mostly in October was a tendency for more blocking to happen up in the northern Latitudes. This is what I’m VERY interested in really. IF that type of scenario comes back at some point over the winter…then we can get a period of time…perhaps 10 days or two weeks where we are VERY vulnerable to significant winter weather.
Let me show you what I wonder about. See those reds and yellows up across most of central and eastern Canada towards Greenland as well…that is high latitude blocking. When the jet stream gets blocked up like that UP THERE it gets deflected more towards the south…and disturbances from the Pacific can come towards the Plains. Those disturbances would then be a key to precipitation production for our area.
The issue then is will there be the cold air to tap into. That remains to be seen BUT there is some hope for snow lovers that even in an overall milder than average winter that there can be threats of significant snows locally.
It seemed last winter there weren’t even that many threats really.
There are other things too…perhaps to be written about in December when we come out with our forecast. I have some other data that I want to show you regarding La Nina…and the fact that this is a back to back year (not that uncommon) of La NIna but this blog is already really wordy and long…so I’ll stop for now
I wanted though at least to get some thoughts out to you since I’ll be on vacation through the middle of next week.
The feature photo is from Vicki Anderson Dolt