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Copy of AST 2

Avalanche Education Course (AST1)
by

ROSS BERG

on 26 November 2015

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Transcript of Copy of AST 2

WELCOME - AST level 1 + 2
Avalanche Education Development
What is an AST 1+ 2?......
AST1
7-8 day course
Professional Qualification
Write down weather observations
Understand snowpack
Minimum 100 days professional experience
14 day course
Usually two seasons to complete
Operations Level 1
Operations Level 2
Avalanche Forecasters & Planners
5 day classroom based course
Operations Level 3
Most people fully buried by avalanches are killed
Most people buried alive suffocate in less than 30 minutes
140 deaths in last 10 years
2008 – 2010: 17 skiers, 35 snowmobilers
Most victims are recreational travelers
The majority of people involved in avalanches started the avalanches themselves!
Numbers
Avalanche Bulletin
Type of Avalanches
Avalanche Sizes
Frequency vs Slope Angle
Name
What do you hope to get out of this course?
What previous experience & training do you have?
Today's Bulletin
Slab Avalanches
Common Start Points
Weather Patterns
Shallow Areas
Convexities
Cornices & Rock Outcrops
How to.....
Weak Layer
Slab Avalanches: Wet, Cornice, Persistent, Wind slab
Trees
Rocks
Size Matters!
Snowpack and Weather
Precipitation
Type
Wind
Temperature
Amount
Intensity
Gradient
Duration
Speed
Snowpack
Direction
Air
Snow
Rain
More than 25cm within a 24 hour
period is a concern
2.5cm/hr of accumulation over 8-10 hrs = instability
Wind for longer period of time = more lee deposits
Lee slopes vs. windward..
Greater than 25 Km/hr causes snow transport
Affects surface layers
Affects precipitation type & crystals
Snowpack temps affect rate of change over time
More than 1°per 10cm of snowdepth change leads to facets
AST2
9 hours of classroom time
Three days in the field
Recognising Avalanche Terrain
Introductions
Indicators
Loading
What are the three main weather effects that influence the snowpack?
Avalanche Terrain
Terrain Traps
Route Finding Exercise
Weather: History creates the snowpack
Changes in Terrain: Terrain modifies snowpack
Time: Constantly re-asses snowpack

Snowpack Structure
Have a visual picture of the snowpack!
During storm: Temp, wind, humidity
Between Storms: Sun, wind, rain affect surface
Temperature: Difference between layers
Snow Crystals Changes
What creates these layers?
ALWAYS CHANGING !!!
Formation of Slab Avalanche
Terrain and Slope Angle
Constant Sluffs
Large Slabs Uncommon
Largest Slabs, frequent avalanches
Dry slabs uncommon, wet avalanches ocassionally
Frequent small avalanches, infrequent slab avalanches
10-25
25-45
45-60
60-90
Constant Sluffs
Large Slabs Uncommon
Largest Slabs, frequent avalanches
Dry slabs uncommon, wet avalanches ocassionally
Frequent small avalanches, infrequent slab avalanches
Rounding
Faceting
Surface Hoar
Run Out Zone
In "Avalanche Accidents in Canada - Volume 4" by Geldsetzer and Jamieson it was reported that in a sample of 184 recreational avalanche accidents, 83% of them occurred on slopes between 25 and 40 degrees and half of these fell in the range from 31 to 35 degrees. (From talk given by T. Geldsetzer, Edmonton, AB, November, 1997)
ATES - Avalanche Terrain Exposure Scale
Develop a systematic approach to terrain evaluation, risk assessment and risk management/decision making

Effectively use the Avaluator Trip Planner and slope Evaluation Card

Develop skills to determine slope specific exceptions to regional bulletin ratings

Be familiar with the ATES Technical Model

Use advanced route selection, terrain identification and travel skills

Be proficient in Companion rescue skills
Are usually small, but may gain significant mass on long steep slopes.
Are typically limited to steep terrain (40+ degrees).
Stabilize soon after a storm, usually within a few days.
Loose dry avalanches are best managed by avoiding terrain traps and large steep slopes until the surface has stabilized. On large steep slopes, occasionally move across the fall line to avoid being caught by your own sluffs from above.
Dry Loose Snow Avalanches
Are more powerful than loose dry avalanches due to their higher density.
Are often limited to sunny slope aspects.
Are commonly confined to the warmest part of the day.
Loose wet avalanches are best managed by avoiding start zones and avalanche paths when the snow becomes moist from daytime heating, from rain, or does not freeze overnight.
Wet Loose Snow Avalanches
Involve wet layers in the snowpack, typically including deeper layers.
Tend to be large.
Occur when water forms or penetrates below the surface of the snowpack.
Wet slabs are best managed by avoiding start zones and avalanche paths when the snow becomes wet from daytime heating, rain, or lack of an overnight freeze.
Wet Slab
May trigger large slab avalanches on relatively stable slopes below.
Are often associated with recent wind loading and/or tempera­ture changes.
Can be triggered from ridges, sometimes breaking surprisingly far back onto ridge tops.
Cornices are best managed by approaching corniced ridges cautiously. Avoid travelling on or near overhanging cornices and limit time spent exposed to slopes below cornices, especially soon after wind events and during periods of warming temperatures.
Cornice Avalanche
Vary in size from small to medium.
Occur on steeper lee and cross-loaded portions of slopes (typically 35+ degrees).
Are often limited to specific terrain features such as lee ridge-tops.
Can often be recognized by the appearance of the snow surface, changes in surface snow hardness, hollow, drum-like sounds and/or shooting cracks.
Winds that vary in strength and direction can produce complex and unexpected wind slab patterns.
Stabilize fairly soon, usually in a few days to a week.
Wind slabs are best managed by recognizing and avoiding areas where wind slabs have formed, until they have stabilized.
Wind Slab
Vary in size from small to very large.
May be soft slabs, fooling people into underestimating slab potential.
Tend to occur on moderately steep slopes (35+ degrees).
May occur in all terrain, but are larger and more frequent in the alpine.
Stabilize soon after a storm, usually within a few days.
Storm slabs are best managed by conservative terrain choices during and after storms until the storm snow has stabilized.
Slide on buried persistent weak layers, which often form during clear periods and may involve deeper layers from multiple storms.
Vary from medium to very large; may cross terrain barriers to involve multiple slide paths.
May occur on very gentle terrain, even slopes of 20 degrees or less.
May be localized to specific elevations, aspects, or regions.
Often no visible signs instability. Lack of avalanche activity and lack of danger signs are NOT reliable indicators of stability.
Compression tests and Rutschblock tests may locate PWLs.
Stabilize slowly, tending to persist for several weeks or longer.
Often go dormant, becoming active again when the weather changes.
Prone to lingering pockets of instability that persist long after most areas have stabilized.
Tend to release above the trigger, making it difficult to escape.
Are often triggered remotely from a long distance away.

Persistent slabs are best managed by very conservative terrain choices. Allow extra time for persistent slabs to stabilize and use a very cautious approach to new terrain. Be especially cautious after storms or during warming periods.
Persistent Slab
Slide on deeply buried persistent weak layers, which often form during clear periods or rain-on-snow events early in the season. Involve thick, hard slabs, sometimes the entire snowpack.
Tend to be very large, commonly cross terrain barriers to involve multiple slide paths.
Tend to occur on larger slopes of moderate steepness, typically 30-40 degrees.
May be localized to specific elevations, aspects, or regions.
Often no visible signs of instability. Lack of avalanche activity and lack of danger signs are NOT reliable indicators of stability.
Stabilize slowly if at all, persisting for months and often the entire season.
Dormant persistent deep slab instabilities often become active again when the weather changes, especially after storms or with warm spring weather.
Tend to release above the trigger, making it difficult to escape.
Are often triggered remotely from a long distance away.
Deep persistent slabs are best managed by very conservative terrain choices and a very cautious approach to new terrain. Be especially cautious after storms or during warming periods.
Deep Slab/PWL
Storm Slab
Decisions-making Support System
Entry-level decision makers
Need support systems for planning that rely primarily on other to determine avalanche danger and terrain ratings
Heavy use of Avulator or apporprate local decision making support system
Intermediate Decision Makers

Have additional training and experience
Get out often to a variety of places where they make decisions and manage risk for themselves an perhaps others
With guidance, can recognize exceptions that allow them to verify local conditions, which may allow travel in places and at time that would fall outside the recommendations made by an entryl-level support system.
Need support from the knowledge of others to provide preliminary guidance
Advanced Decision Makers
Have extensive training and experience
Get out often to many different places making decision for themselves and for others
Have the knowledge required to gather raw data necessary for analysis of avalanche conditions
Have knowledge required to make terrain evaluations
Will this terrain produce an avalanche?
Terrain Exceptions
problem
Where
How to Avoid

Learn essential companion rescue skills
Understand avalanche bulletins
Recognise avalanche terrain
Understand the formation and nature of avalanches
Make good route selection and safe travel decisions
Use the Avaluator as a decision making tool
Full transcript