Winter Snowfall in Rendezvous Bowl: 1974 - 2019

With a week to go before Thanksgiving and the season opening of our local ski areas, it’s safe to say that some folks may be getting a little nervous about the lack of snow and frequency of snowstorms the last few weeks.

After a wetter than normal September, snow began accumulating in the mountains. That was followed by a record cold October, with more snow accumulating up high early and mid-month. Skiers were getting after it on Teton Pass and ski areas were able to crank up the snow-making guns.

A few small storms this past week added a little, otherwise, the first half of November was essentially bone-dry. In order to calm your fears about what’s to come during the meat of the winter, I’m here to update the long-range outlook for December through February.

First predictions

You may remember in early September I did my first outlook for the winter season in this column. Two months ago, just after the Farmers’ Almanacs came out with their predictions, two of those almanac forecasts had us painted under a cooler and snowier winter. Those forecasts don’t change once they are published back in late August.

The Climate Prediction Center, known as CPC, forecast I reviewed from the National Oceanic and Atmospheric Administration (NOAA), issued mid-August, revealed western Wyoming would be warmer than normal, but was undecided about precipitation. That outlook was non-committal about it being above, below or normal for precipitation for the three-month period — they gave it “equal chances” for each. No help there.

Latest data

The newest CPC three-month long-range outlook, issued mid-October, still has western Wyoming under warmer than normal conditions for December, January and February. This is still in direct contrast to both Farmers’ Almanac temperature forecasts.

The CPC’s precipitation forecast has shifted to placing northwest Wyoming under a better than 50% chance of having above normal precipitation. That’s somewhat more encouraging.

El Nino explained

The El Nino Southern Oscillation, or ENSO, is an indicator long-range forecasters use to decide what general conditions for the winter season might be across the Northern Hemisphere.

The ENSO actually has three different phases: El Nino, La Nina and neutral. Sea surface temperatures in the Equatorial Pacific determine the current phase of the ENSO.

El Nino occurs when sea surface temperatures are warmer than normal. La Nina occurs when temperatures are colder than normal. Neutral ENSO conditions, or No Nino, occur when temperatures are near normal, usually when transitioning between El and La phases.

In general, during an El Nino winter the northern tier of the U.S. experiences warmer than normal temperatures and below normal precipitation. At the same time, the southern tier of the U.S. is usually cooler with above normal precipitation.

During a La Nina winter the opposite is true, the northern tier of the U.S. usually experiences a cooler and snowier winter, while the southern tier is usually warmer and drier.

Neutral or No Nino winters could go either way. The ENSO forecast for this winter is for neutral conditions in the Equatorial Pacific.

Winter 2019-20

Last winter was a weak El Nino, and pretty much the entire western U.S. had a cooler and wetter winter. Jackson Hole was above normal for snowfall, after a record February. That wasn’t supposed to happen.

Historically, from snowfall data for the past 44 winters at Jackson Hole Mountain Resort, El Ninos have produced more below normal snowfall winters here than above normal (10 below and four above). La Ninas have produced more above normal snowfall winters than below normal (10 above and four below).

Neutral or No Ninos have also produced more below normal snowfall winters than above normal snowfall winters but by a smaller margin (nine below and six above).

What’s really interesting: two of those six above normal No Nino winters were the two snowiest winters on record at the resort, the winters of 1996-97 and 2016-17.

Based on those stats, an optimist would be rooting for another record breaker during this winter’s No Nino. The pessimist would say chances are less than 50-50 for above normal snowfall.

I already know how many optimists there are — just count how many season ski passes have been sold so far.

Jim Woodmencey is the chief meteorologist at MountainWeather.com and has provided forecasting for the Jackson Hole and Teton range for over 25 years. Contact him via columnists@jhnewsandguide.com.

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