The Avalanche Paths of Teton Pass

As a forecaster, there are multiple avalanche paths on Teton Pass that you need to pay attention to. The following video is an introduction to those paths.

We recommend spending some time studying the avalanche paths on Teton Pass. Below you will find the path descriptions from the Teton Pass Avalanche Atlas and a link to a CalTopo map where the avalanche paths are marked. If you want to put these markers on a google map, you can export the KML file and it should open in google earth. If you choose to use google earth and you know how to use the history slider, 1/2005 shows the terrain snow covered, otherwise 6/2017 shows the best images and is the default.

Now that you have all of the information for your assignment, it is important to understand what we expect of you as you forecast for the pass. As the Teton Pass Avalanche Forecaster, you need to understand the tools that are available to you, including artillery, the gazex, the avalanche guard, and hand charges.

You also need to understand timing for closures, as well as how you communicate with the public. The document below describes tools available to you, as well as communication expectations.

It’s January 17, 2012 on Teton Pass

You are now the WYDOT avalanche forecaster and there is a big storm on the horizon.

You should have spent some time reviewing the season history up to this point, the avalanche activity up to this point, and the pertinent snow pits dug this winter. If you haven’t, DO THIS NOW.

Now it’s time to take some notes…..with the season history and the forecast for January 17, 2012 that you find below, we’re going to ask you to fill out a PM Hazard evaluation form.

It has been a dry season in the Tetons thus far.  It’s quite the shock, as last year was non-stop snow.  The snowpack has virtually flat-lined in January.  The last “storm” you got was 6” and there was a 3-car wait for the tram.  Folks are thinking their luck may change soon.  There are rumors that the flow is “going zonal” and that the Tetons may finally get a big storm.  As a WYDOT worker, you’re looking forward to the prospect of doing something besides studying the weather models and fixing all of your electronics, like you’ve done all winter.

Weather Obs: On January 17, skies started out cloudy and there was 1” of snow overnight. Snow, temperature, and sky cover data is available from the mid-mountain study plot at 9360’ and wind data is available from the top of the tram at 10450’.  Conditions at 0500 are:

HS = 42”HN24 = 1” HNW24  = .08” r = 8% Wind avg = 19 mph Wind DIR = W Wind Gust =45 mph
Temp = -3° CSki Pen = 4”Boot Pen = 16”Sky = OVC

Avalanche Hazard Forecast:

***Note that Morning Rating and Afternoon Rating column headers shifted.***

Avalanche Obs: Yesterday, the Grand Targhee Ski Patrol triggered two slides on a north facing slope at an elevation of 9,000 feet.  HS-AE-D2-O – 24” deep. 100-200’ crowns.

Weather Forecast:

Expect light snow showers to continue ahead of approaching Pacific moisture. Temperature Forecast for 8,000´-9,000´: Rising into the positive single digits. Ridge Top Wind Forecast for 10,000´: Increasing to 25 to 35 miles per hour out the west to southwest. Snowfall Expected Next 24 Hours: 3 to 6″

Based on the information above, as well as the season history you have reviewed, it is time to complete a PM Form. Take your time completing this form. You can only submit the PM Form once. Once it is approved by AAI admin, you will be allowed to move on with this forecasting exercise.

Snow Profiles around Teton Pass during the Winter of 2011/12

Now that you are beginning to build a picture of what the 2011/12 early season looked like, graph out a hypothetical snowpack if you haven’t already. Translating a season history into a hypothetical snowpack is a skill that has to be practiced. Try it now for an easterly aspect at 9000 feet. The goal is to have an opinion. This doesn’t have to be turned in.

Now let’s talk about snow pits dug around Teton Pass during the winter of 2011/12. Here is an introductory video.

Now that you have your sample snow profile, compare it with the snow profiles from the range. Do they line up? If not, what looks different? Do you have an idea about why they vary? Remember, one of the most important skills as a forecaster is to HAVE AN OPINION. You don’t have to be right, but if you don’t have an opinion, you don’t get the opportunity to learn when conditions didn’t match your forecast/opinion.

An introduction to the Teton Pass Forecasting Exercise

This forecasting exercise takes some time. It is an involved, educational exercise that we expect you to do over a couple sessions.

In this section, you are going to be forecasting for Teton Pass. It is January of a lean snow year. The storm cycle that you are forecasting for actually happened, so this exercise is a great learning opportunity. Take your time in completing the exercise. You will be graded on your quiz answers. You will also receive data about what actually happened during this storm cycle.

There are quite a few resources to review before we dive into the exercise. Here is a quick introduction to the weather spreadsheet of the season history up to the date of the storm.

Take the time to study the season history. Consider whether you have the potential for basal facets or depth hoar forming within the snowpack. Look for times when there were dry spells and surface hoar and near surface facets were formed. Look for periods of high winds. Look for storm cycles. It can be useful to develop a hypothetical snowpack based on season history. You will have snow pits to compare your hypothetical snowpack to.

Another resource that you have for this forecasting exercise is the radial plot of avalanche activity. Below is a video introducing the radial plot. We like this tool as it can paint a picture of where avalanche activity is concentrated. It’s important to recognize factors that might bias the data reported including concentration of skiers in terrain (ie. there are a lot more skiers in the Tetons on east, northeast, and north facing terrain than on west facing terrain), skiable terrain, etc..

Take the time to study the avalanche activity that has occurred up to mid-January 2012. What aspects and elevations have seen the most avalanche activity? Have those avalanches been to the ground or have they been shallow soft slabs? This can help you better understand the structure of the snowpack in mid-January.

The Stability Wheel and Avalanche Mechanics Continued.

When looking at if a particular slab, weak layer, bed surface is likely to produce an avalanche, the third component that we look at is friction.

We focus on the friction created between the slab, the disrupted weak layer and the bed surface and if that residual friction can be overcome to produce an avalanche.

Watch the following video to learn more about friction.

The fourth component of the stability wheel is strength. In snowpits, we measure strength by the number of taps that initiate failure in our stability tests. Strength is influenced by many things, including rapid loading, rapid warming, and time.

Watch the following video on strength.

A fifth component of avalanche mechanics and the updated stability wheel is continuity. Greater continuity could lead to larger/wider avalanches 

Continuity is influenced by:

Slab – thickness, extent, hardness 

Weak Layer – size, extent, hardness 

Bed Surface – roughness, extent, hardness 

It is important to study the relationship between the slab, the weak layer and the bed surface. Consider the structure, the propagation potential, the residual friction, the strength, and the continuity of the structure across a slope or mountain range.

Trying to sort through all of this data can be overwhelming at times. Remember, class 1 data trumps everything. If you are witnessing avalanches or experiencing cracking or collapsing, that is mother nature screaming in your ear.

The Stability Wheel and Incorporating Avalanche Mechanics into Assessment

The stability wheel is one way that we think about avalanche mechanics and avalanche release. The four components of the stability wheel include: structure, propagation, friction and strength.

The first component that we are going to talk about is structure. When thinking about structure, we ask, “Is there a path of least resistance?” We quantify this path of least resistance by using the Lemons or 5 components of structure.

Let’s talk about structure:

Another important component of avalanche mechanics is propagation. In order for an avalanche to occur, the slab, weak layer, bed surface combination needs to be able to sustain propagation.

While we can’t evaluate an entire slope, we can dig pits to look for propagation. What we are looking for in stability tests is if the slab, weak layer, bed surface combination can sustain propagation. We use the extended column test, as well as the propagation saw test to look for propagation.

Let’s dig into propagation in this video:

The third and fourth components of the stability wheel can be found on the next page.

The Recipe for an Avalanche, Avalanche Release, and Avalanche Mechanics

When thinking about avalanche release and mechanics, it’s important to return to the foundational question – is there a recipe for an avalanche?

In the following videos, we are going to discuss avalanche release and the components involved in avalanche release. What happens when an avalanche releases is:

  1. Initiation of a failure and fracture. 2. Propagation of this fracture. 3. Fracture of the slab. 4. The overcoming of friction

Crew Resource Management and Risk Management

Have you had a close call or near miss? Have you taken the time to reflect on it? What have you learned from it?

In the following video, AAI instructor Pete Earle, reflects on a near miss that he had a few years ago. Pete discusses the conditions leading up to the day, as well as his communication tactics with his partner. Below are a few communication principles that are important to practice, both in a professional setting, as well as in a recreational setting.

One thing that he learned was the importance of communication and a strategy borrowed from the airline industry, known as Crew Resource Management.

Here is a great paper that discusses 10 Common Missteps of Avalanche Practitioners

You can report a near miss on the Avalanche Near Miss website.

Grain Identification in the Field

This is a deeper dive into field grain ID – what to look for, tips and tricks for easier grain ID, and general thoughts on snow pits and snow metamorphism.

This is not required watching.

Identifying Snow Crystals – Using Shape, Size, Layer Hardness and Weather History

The following video offers some tips and tricks for snow crystal ID. This is something that people often struggle with. The goal of this talk is to offer a refresher for grain ID before arriving at the course. After you watch this video, take time to practice crystal ID in the field, whether it’s in the backcountry, at the ski area, or out your front door.

Here is a link to the International Classification for Seasonal Snow on the Ground This link offers further descriptions for improved crystal ID, as well as additional photos.