Posted: June 5th, 2018
by meteorologist Jim Woodmencey

As some of you may have noticed, I have changed my forecast format on the JH Forecast page. After 25-years of doing my own forecast from scratch, starting at 4:00 a.m. each weekday morning, I have decided to take some of the pressure off, so to speak. Not to mention, the huge amount of time it takes, as well as, the stress and frustration that comes with forecasting the weather.

What you see now on the JH Forecast page, is similar to what I have used on this page on weekends & during vacation periods. However, the data in this version is more refined.

What’s New?

The Forecast info you see initiates from computer models, using the National Digital Forecast Database or NDFD, from the National Weather Service. The NDFD contains a blend of several different models. Versus most other weather forecasts that use only a single model for their forecast display, like the weather app that comes with your smartphone, for instance.

This new forecast format from MountainWeather™ uses the NDFD as a base, to start with. I have hand-picked very specific data for the valley and the Teton mountains and then manipulated some of that data. I have made some adjustments to that data to account for deficiencies that I have identified over the last several years of tracking the performance of NDFD data locally.

I feel this current format is much better than what was being fed to the site before, on my days off. One major improvement for the summer months, is that the forecast now contains a graph of Thunderstorm/Lightning forecast info (similar to what I had in my own forecast). This was not available in the old NWS version used before.

Here is a sample of the new printable version, which puts all the info on to one readable sheet……(available by clicking a button at the bottom of the forecast).

What’s Good?

Advantages of this new format to you are:

1) Forecast is available in the same format every day of the week. No switching back and forth on weekends, holidays, vacation times, or when I am out of town teaching.

2) Forecast automatically updates itself throughout the day and night, as new computer model data arrives. (The old format, mine and NWS, was only updated once a day, at 7:00 a.m.)

3) Forecasts will now be more consistent, 365 days a year.
(I didn’t say they’d be more accurate!)

Some days the forecast will be right, some days it will be wrong. That would true, no matter who is doing the forecast. Something I have learned over the last 25-years!

Have no fear, I will still be keeping my hand in what data is being fed into this forecast and making improvements and adjustments as necessary.

And as far as I know, the JH Forecast on mountainweather.com is still the only place to get a weather forecast for both the Jackson Hole Valley and the Teton Mountains at 10,000-feet, all on one page!

Thanks for being fans of the weather for so many years and I hope you’ll continue to utilize MountainWeather as your source for Jackson Hole’s weather, and beyond.

It looks like the Month of May will finish out with showers, thru Friday June 1st. Then, a Ridge of High pressure builds over the Rockies for dry weather and warmer temps this weekend. That Ridge looks like it sticks around into the middle of next week, with high temps in Jackson reaching back up into the 70’s.

Mountain temps around 10K ft. stay above freezing around the clock this weekend & into early next week, with highs in the 50’s at that elevation.

Map below shows precip exiting the Northern Rockies to begin the weekend. And High pressure building over the Northwest U.S. with no precip expected anywhere nearby.

Map below is for 700mb level (@ 10,000-ft.) for Sunday morning, with Ridge intact and no moisture to be found at that level across the whole Western U.S.
Nice! So get outside & have a great weekend!

Posted: Monday May 28th, 2018
by meteorologist Jim Woodmencey

Low-Pressure over Utah is still in place this morning and is circulating moisture & unstable air around the periphery of this Low. Low is present at the surface,  shown as the red “L” on Sat photo, and the big round “ball” (a closed Low) on the upper level maps. See the 300mb (@30,000-ft.)  jet stream map and 700 mb (@10,000-ft.).

Moisture will still be streaming over northern Wyoming today, Memorial Day, and circulating around that Low-pressure (counter-clockwise rotation) from East to West. Causing more rain & thunderstorms.

Weather will gradually improve through mid-week as this Low moves east into the Plains States.

Posted: Thursday, May 24th, 2018
by meteorologist Jim Woodmencey

After some rainy weather Wednesday, due to a moist and unstable airmass over the western Wyoming, we will finally see some drying the next couple of days. However, do expect some shower activity to return over the Memorial Day Weekend. Best chances for some showers & afternoon thundershowers will be over the mountains, late Saturday thru Monday afternoon.

Why?….Because weak Low-pressure over the Northwestern U.S. will be replaced by weak High pressure on Friday, that sticks around only briefly, bringing the nicest weather. Then an upper level Low-pressure center off the West Coast will move inland and sit over Nevada & Utah later Saturday into Monday, Memorial Day.

Not a ton of moisture evident directly over JH with that approaching Low , but enough to generate some showers, and some chance of scattered thunderstorms, especially afternoon and evening hours as temps will be warmer, 70’s in Jackson Friday & Saturday. Upper 60’s Sunday & Monday with more cloud cover.

Click on the map below to view a cloud & precipitation forecast from the Euro-model, (courtesy of Windy.com). Check it out. Gray is percent cloud cover, the greens/blues are precipitation.

Links to more forecast maps & models can be found on these two pages:
USA Forecast Maps

Computer Models

The ski season is officially over now. Ironically, the deepest snowpack of the season in the mountains often occurs after the resorts are closed. That has been the case at least for the past two winter seasons at Jackson Hole, and for the majority of winters here the last 10 to 15 years.

In this post, I will give you the grand totals for snowfall this winter and also give you an idea of how all that snow stacks-up, compared to years past.

Snowfall

At the Jackson Hole Mountain Resort the season ended on April 8th with around 500 inches of total snowfall. Depending on where you measure that snow.

The Raymer plot above the top of the Gondola at an elevation of 9,360 feet recorded the most snow between October 1st, 2017 and the morning of April 9th, 2018, with 502 inches. Last year that same location, for that same time period, had 521 inches.

The Rendezvous Bowl weather station at 9,580 feet, for the same timeframe this year, reported 496 inches. Last year there was a record 590 inches of snowfall between October 1st and April 9th at Rendezvous Bowl’s weather station.

For historical comparisons, I prefer to use snowfall data from October 1st to April 1st, because there are more years’ worth of data to work with, due to variable closing dates over the years. The total snowfall this season from October through March was 465 inches, compared to 560 inches last season. (Historical total snowfall from October 1st to April 1st is the data plotted on the graph shown.)

What I found to be most interesting, was that this past decade has been the snowiest decade we have seen in the last 40-plus years. No other 10-year period has had more above average snowfall years than this past 10 years or so.

Starting with the 2005-06 winter season, 8 out of last 13 winters came in above the average for snowfall. And that average line has moved up a few ticks in the last decade, as well.

( Data for above graph comes from Bridger-Teton National Forest database).

Snow-depth

The other metric of interest is the maximum snow-depth at the end of the winter season. This gives an indication of how much snow is left up there in the mountains to melt, as we head into May and early June.

The settled snow-depth at the Rendezvous Bowl site on April 1st, 2018 stood at 131 inches. Last year on April 1st, the snow depth was 146 inches.

It continued snowing and accumulating this April, for several days after the resort closed. It looks like we reached our maximum snow-depth on the mountain this year on April 13th, when it peaked at 154 inches in Rendezvous Bowl. That will be the peak, barring any big snowstorms during these last few days of April.

Last year, the maximum snow-depth occurred on April 28th, 2017, with a record depth of 175 inches in Rendezvous Bowl. The deepest ever recorded at this location.

(The above graphs showing snowfall and snowdepths through the last two winter seasons at Rendezvous Bowl, JHMR. Graphs from Patrick Wright at Inversion Labs).

Snow to Runoff

The next thing to monitor in the coming month or so will be the temperatures in the mountains. That will determine how quickly all that snow turns to water. Last year we lucked-out and the melt and runoff was relatively slow, sparing us from any major flooding in the valley.

Currently, as of April 20th, 2018, the snowpack at the Phillips Bench Snotel site on Teton Pass at 8,200 feet contained 33 inches of water, compared to 39 inches at the same time last year.

The Grand Targhee Snotel showed 55 inches of water in that snowpack, at an elevation of 9,260 feet this year on April 20th. That is actually more than last year at this same time, when there was 50 inches of water contained in the snowpack. Indicating that we have a little denser snowpack this year.

More info about snow and water content at the bottom of the Snow Reports Page on mountainweather.com, and historical data and graphs can be viewed on the Bridger-Teton Avalanche Center website.

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