This is my annual summary of the weather for Jackson, WY for the year 2017. At the bottom of this post a re-cap of the weather highlights from 2017 in Jackson Hole.

All data included in this weather summary is taken from the Jackson Climate Station. The historic averages and totals are from the official records, including all years with complete data, between 1905 and 2016.

Precipitation

The total precipitation received in 2017 was 23.27 inches. That is 147-percent of the long-term average annual precipitation of 15.84 inches, or more than ten inches of excess precipitation.

Much of that was due to the very wet & snowy months of January and February. However, September and November were also exceptionally wet, with more than double their respective averages for precipitation.

The wettest month of the year was February, with a massive 5.75 inches of water in town, from rain and snow combined. That broke the old February record of 2.83 inches in 1962, by a wide margin.  On average, February is usually one of the driest months of the year, averaging just 1.14 inches of precipitation.

The driest month of 2017 was August, with less than three-quarters of an inch of precipitation.

Snowfall

No one needs to be reminded that last winter was snowier than normal. January and February 2017 snowfall totals combined were almost twice the norm, 62 inches of snow fell in town those months, compared to an average total for these two months of 33 inches.

Other than that, October 2017 was the only other month for the rest of the year that saw above average snowfall.

We also don’t need to be reminded that December 2017 under-performed in the snowfall department, with just over 8 inches of snow for the month. That is about half of the long-term average snowfall for December, of 17 inches.

The total annual snowfall for Jackson in 2017 was 90 inches. Which actually includes parts of two winters. But, that was well above the long-term average annual snowfall in town of 77 inches.

Temperatures

It was an interesting year temperature-wise in Jackson. Average high temperatures came in below normal 8 out of the 12 months. Whereas, average monthly low temperatures registered above normal 9 out of 12 months.

That is not surprising in a year that had above normal precipitation. A wet year usually translates to more cloud cover, and thus, cooler daytime temps and warmer overnight temps.

In the end, our annual average high temperature in 2017 was 52-degrees, or two degrees cooler than the average of 54-degrees.

The average low temperature for the entire year was 26-degrees, or 3 degrees warmer than the long-term average of 23-degrees.

The annual mean temperature for the entire year of 2017, or the average of the average annual high and low temperatures, calculates out to be 39-degrees. And surprisingly, that was pretty darn close to the long-term average mean temperature for Jackson of 38.5 degrees.

Summary

The weather in 2017 was a little bit wetter and snowier than it was in 2016, and both of the last two years were wetter and snowier than the long-term averages.

At the same time, 2017 managed to maintain what would be considered a perfectly normal range of temperatures. Annual mean temps were identical to 2016, and were also about as close as you can get to nailing the average annual temperature, from the last 100 years of data.

2017 Seasonal Weather Highlights

Winter Season

The Winter of 2016-17 re-set the bar for snowfall in the mountains. It also tested our limits for how much snow we really want to have to shovel or plow in the valley. Beginning in early December 2016, we went from a settled snow depth in town on December 1st of just one inch, to a depth of 18 inches on Christmas Day 2016.

January and February 2017 continued the trend of copious snowfall, tapering off early in March. Almost 100 inches of snow fell in town between December 1st, 2016 and April 1st, 2017. That is well above the average winter snowfall in town of 61 inches.

December and January also saw wild temperature swings. For instance: the low temperature in town on January 6th, 2017 was 32-degrees below zero, that was also the coldest day of 2017. On January 8th, the high temperature was 37-degrees, above zero. A 69-degree swing in two days!

Mountain snowfall was nothing short of huge last winter. At the Jackson Hole Mountain Resort, during the “ski season”, between December 1st, 2016 and April 1st, 2017, the total snowfall was 462 inches. That was from the Rendezvous Bowl study plot at 9,580-feet, which averages 301 inches of snow for this same time period. The only bigger “ski season” snowfall was in 1996-97 with 486 inches. That was twenty years ago.

Total snowfall in Rendezvous Bowl during February alone was 149 inches, making that the snowiest February ever on the mountain.

The single biggest weather event of winter was the storm that toppled the transmission lines on the Teton Village road on February 7th, 2017, during a winter storm cycle like we hadn’t seen since February 1986, some 30 years ago.

Spring 2017

Cold and snowy weather most of the winter, gave way to an early spring. Warmer than normal temperatures in March of 2017 essentially vaporized the snow in the valley. We began the month with 14 inches of settled snow on the ground in town. By March 18th, it was all gone.

Snow was still accumulating in the mountains into April. Enough to push the total winter snowfall number, from October 1st to April 9th, in Rendezvous Bowl to a record 590 inches. That edged out the old record of 585 inches from 1996-97, for that same time period.

April and May 2017 both ended up cooler than normal, but drier than average, in town.

Summer 2017

That theme of cooler-than-normal temperatures extended through the summer. June, July and August all experienced below normal high temperatures.  The hottest day of the year came on the Fifth of July, when it hit 89-degrees in town.

June and July were both wetter than normal, while August was quite dry. August was also a smoky month, from forest fires burning to the west of us in California, Idaho and Montana. People worried that the smoke would be around and ruin the biggest event of the summer.

The Total Solar Eclipse on August 21st, 2017 was that event, and a very weather dependent one. Luckily the smoke had departed before the big day. However, a band of high overcast clouds came over Northwest Wyoming very early that morning, which could have potentially dimmed the viewing experience.

Fortunately, those clouds exited off to the southeast of Jackson Hole an hour or so before the start of the eclipse, and we had as clear of view of this incredible spectacle as you could hope for.

Fall 2017

Summer came to an abrupt end, on the last day of summer. The high temperature in town on September 21st, 2017 was only 41-degrees. That was a record cold maximum temperature for that date. Making it the coldest last day of summer ever in Jackson.

With that cold, came our first dump of snow in the mountains, coating them completely white, top to bottom. September went on to be much wetter than normal in town with almost 3 inches of water, more than making up for a dry August.

October was near normal precipitation-wise, then November stepped up to register almost twice the average precipitation. Temperature-wise, September and October were both colder than average. November was just above average.

We shoveled snow in town in both October and November, and backcountry skiing commenced very early this fall on Teton Pass. Snow depths reported at the upper elevations of the Jackson Hole Mountain Resort exceeded four feet by Thanksgiving.

A drought early this December, with no new snow between December 6th and 13th, 2017, had folks worried about a brown Christmas. Snow during the days leading up to Christmas weekend helped the skiing conditions up high, and provided a White Christmas in town.

Along with milder temperatures, it was certainly a much different December than we had in 2016.

Jim is the chief meteorologist at mountainweather.com and has been forecasting the weather in Jackson Hole and the Teton Range for the past 25 years.

Note: The contents of this post first appeared in the Jackson Hole News & Guide On January 3rd & January 17th, 2018.

During the last week of December 2017 the computer models performed so poorly, by grossly over-forecasting snow accumulation over the northern Rockies, that I was about to give up on them.

This week is a different story, they all handled the situation this second week of January very well. If anything, they under-forecasted snowfall amounts this week.

Jackson Hole Mountain Resort and Grand Targhee Resort received 10 to 16 inches of new snow just in the last 24-hours. And, 24 to 30 inches total for the week!

Below is the Snowfall accumulation Forecast from the NAM Model,
for Thursday a.m. to Friday, courtesy of NexLab: Click pic to play video.

Below is the Snowfall accumulation Forecast from a HiRes WRF Model,
courtesy of CAIC: Click pic to play video.

Pretty right-on this week.

Whew!

Post by Meteorologist Jim Woodmencey

In my 25 years of forecasting the weather for Jackson Hole and the Teton Mountains, I have never experienced a forecast period that was as big a bust as this past week. Between the Christmas and New Year’s Weekends, as much as two feet of snow was forecast, and less than 6 inches accumulated.

In my more than 30 years as a meteorologist I cannot recall a time when the computer models were this far off in their guidance. Not just one model, all of the computer models that I consulted (7 different ones) had forecast copious amounts of moisture and mountain snowfall. They were all wrong. Thus, so was I.

In a December without much snow, the promise of a big dump is taken seriously in a ski town. And, I don’t take it lightly when it doesn’t materialize. Especially when it seemed to be a sure bet that the Teton Mountains would get plenty.

Maybe not the huge dumps like we were getting last December (2016), but in relative terms, a foot of new snow means a lot.

First No-Show

The first busted forecast was on Wednesday, December 27th. I had forecast 3 or 4 inches in the mountains during the day and another 2 or 3 inches Wednesday night. I figured over that 24-hour period the Tetons would see between 5 and 7 inches of new snow above the 9,000-ft. elevation. The mountains got one inch or less.

Second No-Show

The next round of moisture was scheduled for Friday and Saturday, December 29 and 30. I had forecast 4 to 6 inches during the day Friday and another 2 or 3 inches of snow Friday night, for a total of between 6 and 9 inches for the 24-hour period. Some mountain locations got 2 inches, others received just a trace.

Third No Show

On Friday morning, it looked like the jet and the colder air to to the north of us would finally shift further south. After painstakingly scrutinizing all the models (about 7 different ones!), they were all very consistent in forecasting more than a foot of new snow over the next 48-hours.

I decided to go with 5 inches during the day Friday, a break Friday night, then another 5 inches in the mountains on Saturday, as a cold front pushed through.

The mountains got 2 inches at the higher elevations, for the 2-day period.

Instead of, “third times a charm”, it was “three strikes, you’re out”.

All total, from Wednesday morning December 27th to Saturday afternoon December 30th, 2017, the mountains around Jackson Hole received only 5 to 6 inches of new snow.

The computer models had anywhere from 18 to 30 inches of snow forecasted for the same time period in the Tetons.

An example above of a Hi-resolution snowfall model that went bust.

Better Models? Really?

It is frustrating when you have a consensus in all the models, and then they all fail. The weather models available today are more numerous and more sophisticated and have way more data inputted into them, and the detail in the output is far superior than anything I had to work with 25 years ago. It makes me wonder, how can they be that far off in their predictions?

On many days, there is variability from one model to another, especially where precipitation amount is concerned. On those days, you work with the model that has been performing or initializing the best. However, on days when all the models are in agreement, your confidence as a forecaster goes up, because that must be what is going to happen!

In this case, all that confidence evaporated, literally, as hardly any of that forecasted new snow materialized, compared to the amounts the models had predicted.

It is the worst thing that can happen to a forecaster. We call it, the “crying wolf syndrome”. If you are wrong too many times, the public stops believing what you say. It’s crushing when you are wrong.  Rather than “crushing it”, when you are right.

I hope this was an isolated incident and that I can regain some confidence in these models in the future. But after 25 years in the forecast saddle, I have to say, that I was ready to just give it up after this past week.

Another example above of one computer model’s snowfall forecast.

Technical Synopsis

It seemed like we were lined up pretty good, with a strong Westerly flow aloft carrying Pacific moisture inland. But a few things were not happening.

Mainly, the jet stream, the colder air aloft, and the best mid-level moisture that was to be lifted over the mountains, did not get as far south as predicted by the models.

The other part of the equation that the models may have missed is that the atmosphere was not unstable enough, and the strong flow aloft actually caused more of a downslope or Chinook-like wind situation. Rather than lifting the moisture, it was being suppressed, or forced downward.

That would also explain what was responsible for the warming temps in the valley. They stayed in the upper 30’s to around 40-degrees, day & night from Thursday into Saturday.

Unfortunately, I discounted that lack of instability in the airmass, and missed the possibility of downslope winds. I should have paid closer attention to those factors.

Instead, I may have been guilty of one of the cardinal sins of a powder skiing meteorologist, “Thou Shall Not Wishcast”!

Now that I have seen this situation, I will not forget it, and hopefully I will not miss it the next time around. No matter what the computer models are predicting.That is, if I can stay in the saddle.

Posted by mountainweather.com meteorologist Jim Woodmencey