JACKSON, Wyo. – Following three consecutive La Niña winters, El Niño conditions developed in the Pacific Ocean this past spring and summer. As of early November, we have now entered a “strong” El Niño phase, which tips the odds in favor of a warmer and drier winter compared to average in the Tetons.
What is El Niño?
El Niño is defined as the warm phase of the El Niño Southern Oscillation (ENSO), which occurs when ocean temperatures in the central and eastern equatorial Pacific are warmer than average.
This is the opposite of a La Niña, which occurs when ocean temperatures are colder than average. When ocean temperatures are within 0.5ºC of average, this is considered to be a neutral phase.
Over the past three months, the average sea surface temperature in the central and eastern equatorial Pacific has been 1.5ºC above average. Further warming is expected in the coming months, which means this will be considered a “strong” El Niño.
Strong El Niños are defined as those in which sea surface temperatures are at least 1.5ºC above average for three consecutive three-month overlapping periods.
Most climate models are expecting a strong El Niño to persist through the winter months, before weakening in the spring and possibly transitioning into a neutral phase by summer 2024.
El Niño and Recent Summer/Autumn Weather in Jackson Hole
We have actually been in an El Niño phase for quite a while now. Conditions quickly transitioned from La Niña to El Niño back in the spring, with El Niño conditions emerging as early as May.
Historically, El Niño conditions that develop in the summer tip our odds in favor of above-average summer rainfall with roughly equal chances of above or below-average rainfall in the autumn.
This past summer turned out to be very wet in Jackson Hole. In fact, the town of Jackson experienced its wettest June-August period since 1997 (which, by the way, was also an El Niño summer).
The wet pattern has continued into the autumn months this year as well, as rainfall was above average in both September and October. The first week of November featured wet conditions as well.
I have recorded 10.07 inches of precipitation (rain and a little bit of melted snow) in my rain gauge in Jackson (Cocorahs WY-TT-40) since August 1. This is over 50% of our average annual precipitation in Jackson, and this fell in just over 3 months. Average annual precipitation in Jackson is 17.44 inches, for perspective.
Bottom line – we have experienced a very wet summer and autumn in Jackson (and this on the heels of a snowy winter), and it’s possible the emerging El Niño may have been a factor.
El Niño and Winter Weather in the Tetons
While El Niño may tip the odds in favor of a wetter-than-average summer, the opposite is true in the winter. Based on similar winters with moderate to strong El Niño conditions over the past 40 years, the odds lean slightly toward below-average snowfall and above-average temperatures in the Tetons.
The storm track during El Niño winters tends to favor the West Coast and the Southwest, with lighter snow compared to average for the Northern Rockies.
Precipitation (rain and snow) is also more likely to be below average during the spring months (April-May) in El Niño years, even when El Niño is weakening which often happens at this time of year.
Also, temperatures are more likely to start out on the colder side of average early in the winter in November and December, before trending warmer than average from January through March.
Learn More: Here is a detailed analysis I wrote about Jackson Hole Mountain Resort and historical El Niño winter snowfall for OpenSnow.
Caveat – No El Niño Winter is the Same, and There Are Exceptions
El Niño may have some correlation with below-average snow seasons in the Tetons, but it is by no means a guarantee. There have been deep El Niño winters in the past, and it’s always a possibility – even if the odds are lower.
For example, the last El Niño winter occurred in 2018-2019. While this was only a weak El Niño, we ended up with a huge winter in the Tetons that featured heavy snowfall and well below-average temperatures. In fact, February 2019 was the snowiest February on record in Jackson Hole.
The last strong El Niño in 2015-2016 also resulted in slightly above-average snowfall in the Tetons at Jackson Hole Mountain Resort, though temperatures were warmer than average (especially during the second half of the winter).
Conversely, La Niña winters tip the odds in favor of above-average snowfall in the Tetons but it does not always work out this way. Last winter (2022-2023) was a huge winter, but the winter before that (2021-2022) was an example of a poor La Niña season in terms of snowfall.
Also, even if this winter does turn out to be drier than average, that doesn’t mean there won’t be periods when we do receive a lot of snow or very cold temperatures. Climatologically speaking, winters in Jackson Hole are long, cold and snowy after all.
Also, there are other oceanic-atmospheric connections that influence winter weather patterns which cannot be predicted months in advance the way El Niño and La Niña can.
November Weather So Far and the Pattern Ahead
November is off to a mild start in Jackson Hole with temperatures running nearly 5-6ºF above average so far this month in the valley. The last five days of October were colder than any day we’ve experienced so far in November. We also have yet to receive more than a dusting of snow (0.2 to 0.4 inches to be exact) in the town of Jackson.
The first week of the month featured several storms involving subtropical moisture that resulted in low-elevation rain and wet/dense snow confined to the higher elevations.
Snow totals above 9,000 feet have ranged from about 1-2 feet so far this November, but rain crusts have been noted in the snowpack up to 9,000-10,000 feet per the Bridger-Teton Avalanche Center.
While lift-served ski season is right around the corner, the pattern is only expected to turn slightly colder and more active between now and Thanksgiving weekend.
A few light snow showers are possible on Thursday, but expectations are low as we will be right on the edge of the storm track.
A storm will approach our area from the northwest this Sunday (November 19) and is expected to produce light to moderate snow at the moment, though this could change between now and then. Temperatures will trend colder, but valley snow accumulations will still be tough to come by.
Here is a snowfall projection from the European Model over the next 7 days:
Early next week, we will head back into a drier pattern then it’s possible we could see another shot of snow around Thanksgiving.
Alan Smith, Meteorologist
