All posts by Jim Woodmencey

More Snow, No Foolin

A potent storm system in the Gulf of Alaska will bring snow to the mountains of the Pacific Northwest and Northern Rockies today through Tuesday, lingering into April Fool’s Day.

Map below shows position of Low-pressure Monday, March 30th and forecast position on Tuesday March 31st. Jet stream also pushes inland across Oregon, Idaho and western Wyoming through Tuesday, bringing lots of Pacific moisture in a strong Westerly flow aloft.

This storm system brings progressively colder air with it, causing snow to progressively lower elevations though Tuesday night. Very unstable atmospheric conditions will also cause some thunderstorms to develop.

By April Fool’s Day, it looks like snow accumulation in the mountains (especially above @ 9,000-ft.) will be significant: Oregon & Washington Cascades = 24 to 30 inches Central Idaho mountains= 12 to 18 inches. Tetons, Absaroka & Wind River Ranges= 12 to 18 inches also possible.

Snow Forecast Maps

Map below shows one computer model forecast of snow through Wednesday morning, April 1st.  (From CAIC WRF model).

Map below shows another computer model snowfall forecast for the same time period. ( From COD NexLab NAM model).

Look like March will go “Out Like a Lion” this year, across the Northwestern United States.

Post by meteorologist Jim Woodmencey

Jackson Hole Winter 2019-20 Review

The “meteorological” winter season is officially ended, defined by the months of December, January and February. The astronomical winter season, which began on the Winter Solstice (December 21st, 2019), runs until the Spring Equinox on March 19th this year.

Below is a re-cap of all the highs and lows and snow that we experienced here in Jackson Hole this winter season.

December 2019: Cold and Dry

In the Town of Jackson, temperatures this past December were colder than normal. The average high temperature was 27-degrees, two degrees below average. The average low temperature for the month was 2-degrees, which was five degrees colder than December’s long-term average low temperature.

Precipitation and snowfall were both well below normal in December in town, with 0.82 inches and 11 inches, respectively. Average precipitation in town in December is 1.52 inches, whereas, the snowfall averages 17 inches.

The mountains were also behind in the snowfall department during the month of December. At the Jackson Hole Mountain Resort, at the Rendezvous Bowl study plot (at the 9,580-foot elevation), total snowfall in December was only 68 inches, compared to a long-term average snowfall in December of 81 inches.

January 2020: Warm and Wet

Where December lagged behind, January more than made up for it, in both temperature and precipitation.

Cam Fitzpatrick shreds January’s Powder
on Togwotee Pass

In town, the Jackson Climate Station had an average high temperature of 30-degrees this January, which is three degrees warmer than the long-term average high. The average low temperature in January 2020 was almost 14-degrees, 13.6 F to be exact. That is nearly ten degrees warmer than the long-term average low temperature in January of 4-degrees.

Precipitation was well above the average, with 2.06 inches in town in January, more than a half-inch above the long-term average of 1.52 inches. Snowfall also exceed the average this January, nearly twice the long-term average. January 2020 had 36 inches of snowfall recorded in town, compared to an average in January of 19 inches.

The Jackson Hole Mountain Resort had a banner January for snowfall, shattering the old January snowfall record. The Rendezvous Bowl site recorded 169 inches of snowfall in January 2020, blowing past the old January record of 150 inches from January 1998. To put that in perspective, the average snowfall in January up there is 87 inches.

January 2020 became the third snowiest month ever recorded at JHMR. Only December of 1996 with 225 inches, and February of 2019 with 196 inches, had bigger monthly snowfalls on the mountain.

February 2020: Cold and Snowy

February began looking like it might be a warm one, with high temperatures in the lower 40’s the first two days of the month. That was just a tease, as the Town of Jackson Climate Station recorded an average high temperature this February that was a full four degrees colder than normal, 28-degrees versus 32-degrees.

The average low temperature this February was 0.6-degrees, which was also much colder than normal, nearly seven degrees colder than the long-term average low temperature in Jackson of 7-degrees.

The coldest day of the Winter of 2019-20 was on February 20th, 2020 when it got down to 25-degrees below zero. That also tied the record for the coldest temperature ever recorded in Jackson on that date, tied with February 20, 1955.

Precipitation in town came in below average by only a tenth of an inch. However, snowfall in February was above average, with 20 inches recorded versus our average February snowfall of 14 inches.

February 2020 snowfall in the mountains was also above average, with 94 inches at the Rendezvous Bowl site compared to the historic average of 73 inches for the month of February. Nowhere close to February 2019’s record snowfall of 196 inches.

The author in deep on “25-Short” in GTNP early February 2020

Summary: Colder & Snowier than Normal

Overall, the average high and low temperatures in the Town of Jackson were colder than normal for the meteorological winter of 2019-20. Each registered one-degree Fahrenheit below the historic averages for that three-month period.

Precipitation ended up only a quarter inch shy of average, with 3.91 inches versus the average total precipitation for December through February of 4.16 inches.

Snowfall was resoundingly above average this winter in town, with 67 inches of snowfall recorded at the climate station, compared to the long-term average for December through February of 50 inches.

Mountain snowfall also checked in with a total for the three-month period of 331 inches. That was a little less than last winter’s 365 inches for the same time period. Although, this winter still received 90 inches more snow than the historic average snowfall total for December through February, of 241 inches at Rendezvous Bowl.

Post by meteorologist Jim Woodmencey

Most of this post originally appeared in the March 11th, 2020 issue of the Jackson Hole News & Guide.

Record March Snowfall in Jackson, WY

On the last day of this Corona-Virus-shortened ski season the Town of Jackson and the Jackson Hole Mountain Resort both broke snowfall records. That happened just when we thought spring was arriving early this March.

Town Snowfall Record:12 inches of new snow was recorded at the Jackson Climate Station on the morning of March 15th, 2020. That 24-hour snowfall was recorded between 9am Saturday & 9am Sunday, March 14 to 15. That broke the old record for this date of 5.5 inches in 2006.

That also exceeds the previous “official” one-day snowfall record for the month of March in the Town of Jackson of 10 inches, from March 17, 1971. Jackson only averages 11 inches of snow for the entire month of March.

Note: There is one other snowfall recording from March 12th, 1906 that showed 12 inches in one day, and another from March 25th, 1907 that showed 14 inches in one day. These recordings are not from the Town of Jackson, but from an unverified location on a ranch outside of town, possibly near Ely Springs.

Precipitation: In the precipitation department, the Jackson Climate Station received 1.15 inches of water in that snow recorded on Sunday morning March 15th, 2020. That is the second greatest one-day precipitation amount ever recorded in one-day during the month of March, behind March 3rd, 1995, when 1.80 inches was recorded.

Data sheet from Jackson Climate Station


JHMR Snowfall Record:At the Jackson Hole Mountain Resort, at the Rendezvous Bowl Site ( 9,580-ft.) 23 inches of snow was recorded on the morning of March 15, 2020. (measured from 5am Saturday to 5am Sunday March 14 to 15). That exceeds the old one-day snowfall record up there for that date of 16 inches, from March 15, 2016.

Data from Bridger-Teton National Forest

The Storm that Brought The Snow

Below is a Satellite Image showing the Low-pressure that is parked along the Northwest Coast rotating Pacific moisture inland from California to Wyoming the last 2 days. The center of that Low will shift south along the West Coast the next 2 days, bringing Jackson, WY lesser amounts of snow trough the early part of the coming week.

Posted by meteorologist Jim Woodmencey

Snow in a Northwest Flow

You may not be aware of it, but today, February 5th is National Weatherpersons Day. Celebrate with your favorite meteorologist, buy him or her a beer! This is also the beginning of a steady Northwesterly flow or “Dirty Ridge” event for the northern Rockies.

As a Ridge of High pressure parks off the West Coast and a stream of moisture rides up and over the top of that Ridge, it mixes with relatively cool air from the Gulf of Alaska to make a good period of orographically enhanced snowfall.

In layperson’s terms, that means the mountains get a good dump of relatively low-density powder. Situation and snowfall accumulation forecasts below.

Satellite Wednesday AM

Wednesday Morning Satellite view with flow in black and Ridge marked with blue H.

Short-Term Snow Forecast: Wednesday

This model might be over-forecasting the snow a bit…

Longer Term Snow Forecasts: Wednesday-Saturday

I will update this again Thursday, as a good looking little Low-pressure system moves into Washington & Oregon, bringing a West to NW flow over western Wyoming later in the weekend. That’ll keep the powder coming.

Post by meteorologist Jim Woodmencey

2019: Coldest Year on Record for Jackson, Wyoming

If you lived in Jackson for the last 12 months or so and I were to ask you to name three things you remember about the weather in 2019, the top three answers likely would be: 1) February was really snowy. 2) Summer was too short. 3) October was really cold.

Correct on all counts. But what you really wouldn’t know, without running all the numbers, was that 2019 was the coldest year ever recorded in Jackson, WY.

I could hardly believe it myself when I first sat down to compile the weather stats from 2019. I ran the numbers three times, I went back and dove deeper into Jackson’s weather records. I checked, double-checked and triple-checked, but there it was, 2019 ended up the undisputed champion, now holding the title as the “Coldest Year on Record”, for all of the years that we have complete weather records.

High Temperatures 2019

The average high temperature for the entire year in 2019 was 49-degrees. That is a full five degrees colder than the long-term historic average annual high of 54-degrees.

That made 2019 the new record holder for the coldest annual maximum temperature in Jackson. The old record was 50.4-degrees, from more than 50 years ago, in 1968.

Also of note, every month of the year in 2019 had colder than normal average high temperatures, except November, which ended up right at the long-term average.

October 2019 blew its average high temperature record off the charts, with an average high temperature for the month that was 13 degrees colder than the long-term average.

With all those cold temperatures, perhaps you had forgotten that the hottest day of the year was on July 23rd, 2019, when it reached 87-degrees.

Low Temperatures 2019

The average low temperature for all of 2019 was 22-degrees (21.73-degrees to be exact). That is one degree colder than the long-term historic average of 23-degrees.

In 2019, there were only three months that had an above average minimum temperature, April, July and September. June and August came in right at normal for monthly low temperatures.

The coldest day of the year in 2019 was 25-degrees below zero on January 1st. Also of note was the coldest temperature ever recorded in the month of October, when it dropped to 6-degrees below zero on October 30, 2019. I’ll repeat, that is the coldest temperature ever recorded in Jackson in October.

Last year ranked as the 10th coldest year on record for annual minimum temperature. Nothing too remarkable there.

What was remarkable, was how many days of below zero temperatures Jackson experienced in 2019, 62 days. It ranked as the 3rd most days in a calendar year, in our recorded history. The last time we had that many below zero temperature readings was in 1952.

Below is a graph of the number of days each year that the minimum temperature was below zero Fahrenheit.

Mean Temperature 2019

If you take the average of all the high temperatures and all the low temperatures for the year, you get what is called the annual mean temperature. This is perhaps the best gauge of the overall temperature for the entire year.

In 2019 the mean temperature for the year was precisely 35.36-degrees. Rounding that number up to one decimal point, to 35.4 degrees, it still beats the old record.

The old record coldest year in Jackson was 1944, which had a mean temperature of 35.5 degrees. The average high temperature that year was 51.5-degrees and the average low temperature was 19.4-degrees.

Keep in mind, to be in the competition for coldest or warmest year ever, you need 12 full months of complete weather data. There are many years, in the last 100 years, with too many missing days or months of data to even be considered as a qualifier.

It is the annual mean temperature that distinguishes 2019 as the coldest year ever recorded in Jackson.

Below is a graph of all the years which had complete records, spanning from the earliest year 1923, through the latest year 2019.

From this graph it is quite obvious that the 1990’s to early 2000’s were some of the warmest years and that the 1950’s to early 1970’s were some of the coldest. The all-time warmest annual mean temperature in Jackson’s climate record was 47.5 degrees, back in 1933.

Precipitation Above Normal, Again

We are now into our fourth year in-a-row that the Town of Jackson has experienced wetter than normal conditions, by an annual measure.

Jackson’s long-term average annual precipitation is 15.83 inches. In 2019, the total precipitation in town was 18.17 inches.

It should be noted that in January of 2019 there was over two weeks when precipitation and snowfall were not measured, due to the government shutdown. So, the numbers for these annual totals are a bit lower than what actually accumulated.

Fortunately, the temperature record was complete, because a number of years ago the NWS switched the climate stations over to a digital recording temperature system.

2019 Snowfall Highlights

Total snowfall in the year 2019, from January through December, was 111 inches, not including the snowfall that was missed in mid-January. That is still well above the long-term average annual snowfall in town by nearly three feet! The long-term average annual snowfall in town is 77 inches.

That also makes it four years in-a-row with above normal annual snowfall in the Town of Jackson. Keep in mind, the annual snowfall number spans parts of two different winters.

February 2019 saw record breaking snowfall, with 55 inches in town. That blew away the old snowfall record for February of 33 inches, set back in 1978.

That 55 inches was also the second snowiest month ever recorded in town, falling just shy of the 56 inches that accumulated in January 1969. And February is a short month!

Jackson Hole Mountain Resort also experienced their snowiest February on record, with 149 inches. That was also their second snowiest month ever recorded, behind December of 1996, which had 225 inches.

Winter Snowfall History

A better way to look at snowfall numbers is to use totals from the actual winter season. Graphs of winter season snowfall are shown below, for the Town of Jackson and the Jackson Hole Mountain Resort.

Winter 2018-19 was the 6th snowiest in Jackson’s history.

Winter 2018-19 was the 5th snowiest winter in Jackson Hole Mountain Resort’s historical records, kept since 1974-75.

Summary

It was an amazing feat to string together 12 consecutive months to crown 2019 as the coldest year ever recorded in Jackson. That, in a year which was also wetter and snowier than normal. A very memorable year, with some new records that will be hard to beat.

If you study the graphs provided, it is easy to see the recent trends in Jackson’s historic weather records. Over the last 5 to 15 years, they carry a theme of colder temperatures, more annual precipitation and more snowfall.

Post by meteorologist Jim Woodmencey