Pete Parsons recalls epic cold snap of December 1972

Presenter: Pete Parsons offers the seasonal climate forecast for October, November, and December 2026. 

Pete Parsons (ODF): Hey, I’m meteorologist Pete Parsons with the Oregon Department of Forestry. Welcome to the seasonal climate forecast. One of the things we do is go back and look at the past to try to predict the future. 

This is an analog-based forecast method: Find years in the past with similar tropical Pacific Ocean temperatures to the current year, see what happened in those years, and that helps us to see what may happen this year.

It’s a very good method for getting some information beyond where the short-term dynamic models can forecast. They’re real good out to about a week, and then they decay very rapidly after that. They don’t track the energy very well.

This has limitations too. We have very few analogs to pick from. We only have good ocean temperature data like this back to about 1950. That’s only just over 75 years of data. That’s nothing when you’re looking at data sets. That’s a limitation. But we work with what we have.

We’re going into a very strong El Niño. And in fact, as I mentioned, we have records back to about 1950. The Climate Prediction Center of NOAA says this is likely going to be the strongest El Niño we have seen since records began back in 1950.

And we’ve also got, in the North Pacific, a cool phase of what we call the Pacific Decadal Oscillation. Normally, you don’t get the cool phase of the Pacific Decadal Oscillation and really strong El Niños. So this is kind of an odd duck year.

We’ve only got a couple of years that have even closely resembled this. And those are the ones that I picked for my analogs, and so far they’re working out well because they picked the transition to this cooler, wetter weather in September that we got.

So I’m sticking with them for one more month.

Unfortunately, those years begin to diverge with their solutions. So I’m not going to be able to hold on to them all the way through the winter. In fact, I’ll probably have to update at least one of them next month because they start to do different things and one of them’s going to be wrong, you know, pretty wrong.

The’81-’82 and ‘71-’72, they kind of behave in a similar fashion going forward. And 2023 is going to give a different solution. It wants to revert us back to warmer and drier weather going forward, whereas these ones want to stay wetter and at least average temps or maybe a little cooler than average.

So something’s going to give here. We’re going to have to make some adjustments going forward.

But that’s where we are right now. So I use a blend, a straight mathematical blend of those years, how going forward, their precipitation and their temperatures compared to their 30-year normals, which are going to be different from the current 30-year, especially for the older years, and then take a blend of those going forward.

We’ll see how that works out. So using those three years, NOAA’s got a nice tool. You can generate a composite upper air map or what you often see on your television broadcasts.

For October using 1972, ‘82, and 2023, the mean pattern shows some ridging along the West coast in October. But notice that there’s kind of a split flow developing, one branch of the jet stream down here starting to strengthen, another branch up here.

That is a classic El Niño signature with a split flow in the jet stream; a whole lot more jet stream energy or troughing coming into California. That’s also a sign of El Niño developing.

So we are expecting some pretty significant storminess into California as we go into the fall and the winter, relative to average. And I know they’re preparing for that. We can get beach erosion. A lot of things going on down there.

The question is going to be: How much of that is going to translate up north into Oregon?

1972 and ‘82 had more of that jet stream energy translating north into Oregon than did 2023, going forward. So we’ll see which ones of those tend to play out better. That’s going to be a general theme this winter. 

Classic of El Niño. Southern Oregon is likely to get more precipitation relative to average than northern Oregon. That’s the way El Niño plays.

Let’s go forward into November. A lot of energy coming into the West Coast, especially into California. How much of that makes it up into Oregon is a question mark, but Southern Oregon has a chance of getting more storm activity than Northern Oregon relative to average.

That’s classic El Niño. And this could be really good news for drought-stricken areas of the southwest U.S. as we pour some Pacific moisture into the southwest. 

So El Niños are not like, ‘Oh, it’s terrible. It’s El Niño.’ No, no no no, it’s all part of the cycle, the water cycle. So it can be good news that way.

Temperaturewise: Near average with a blend. But again, 2023 was the warmest of them all. If that turns out to be the good year and these other two, we’ve got to kind of maybe toss away, we’re going to have to upgrade things warmer next month or the reverse.

But I don’t anticipate keeping all three of these years next month because they start to do different things. Notice how we’ve gone a little bit dry. That’s a classic El Niño signature for Oregon, especially northern Oregon—a little bit drier than average.

I know we’ve got our drought, and so that’s not the greatest news because November is like our wettest month for many areas. And here we’re below average for the precipitations. Argh! Not the greatest.

December: We have a chance of some Arctic air getting in here because of that cold Pacific Decadal Oscillation, you can get Arctic air masses to come in here even during an El Niño. It’s happened in ‘72. It did happen.

And actually in the ‘23-’24 winter, it happened in January of ‘24.

So in the two winters that had a cold PDO and a strong El Niño, both of them gave an Arctic outbreak for the Pacific Northwest, one in December, one in January. 

The one in December ‘72 was epic. Epic! I mean, we had about two weeks of Arctic air. It was one of the coldest outbreaks of the century. And the Willamette Valley—Eugene and Salem—went down to 12 degrees below zero in December. 

I’m not saying that’s going to happen this year, but I’m just saying that there is the possibility of a really cold outbreak.

Now, why so cold in December? Remember when we had that heat wave back in June a few years back? It was right near the summer solstice, and that made a big difference in why it got so hot. If you get a cold spell in December near the winter solstice, it makes it that much colder. 

And that’s why the record low temperatures in the Willamette Valley are in December. The coldest time of the year for the northern Hemisphere is in late January. But our all-time record lows in the Willamette Valley are in December because of the low sun angle. 

And then you get a cold air mass. You have the longer nights. How about that? That’s why that’s one of the reasons it was so hot in June. It was right at the peak. The high sun angle.

Now, Portland’s a little odd duck that way because our coldest temperatures came in in February of 1950. And that’s because Portland in these cold air outbreaks in December tends to be windy because of the east wind coming out of the gorge and that keeps the air mixed, so you don’t get the cold layer right at the surface. 

But farther south, in the valley, away from that gorge wind, that’s when you get the cold temperatures. So it’s kind of a localized thing, but the air masses in general are really cold coming down in late January, February.

And you can get cold, obviously then. But having that low sun angle makes a difference. So we’ll see if we get a cold air outbreak like we did in ‘72 in December. And if so, we could get some real cold temperatures, quite a bit of snow associated with that as well.

I know that probably doesn’t help you a lot, but I wanted you to know there is the threat this winter of a cold air outbreak either in December or January especially, but the rest of the winter outside of that, with the El Niño pattern, is likely to be mild with the precipitation focus over southern Oregon.

We’re going to develop a split flow, one branch of the jet into California, another branch up into Canada. There’s going to be enhanced troughing that’s coming into the West Coast aimed at California, some of it likely making it up into southern Oregon. The door is open for cold air masses, or one big one, perhaps, to drop down into the Pacific Northwest in December or January.

I’m not saying it’s going to happen, but the door is more open for that this winter than in a typical El Niño winter. And if we get it, it can be pretty darn potent, especially when you’ve got systems coming in on that southern branch, which once you get the cold air in here, when you’ve got El Niño, it’s very difficult to get it out of here without making a mess, freezing rain or snow.

Because all of that jet stream energy going into California draws the cold gorge east winds and offshore flow and throws moisture over the top of it as you get out of it. It’s a mess. So there’s potential for that.

For the three-month period: Temperatures near average. They skew a little colder because of that big cold air outbreak in ‘72. 

We’ll have an update next month and we’ll get a little more clarity seeing how these analogs perform here in the month of October and which one or ones we have to throw out and change. 

I had a viewer ask, ‘Hey, can you put up a summary page?’ It summarizes in general what I’ve already talked about here. You can just Google Oregon Department of Agriculture and then go to the Natural Resources tab and you’ll get it.

Happy fall and we’ll catch up with you again next month. Take care.

Presenter: Pete Parsons says similar conditions in 1972 led to an epic cold spell. The temperature in Eugene and the Willamette Valley dropped to 12 below. We’ll check in with Pete again in late October.