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ALPTRUTH

ALPTRUTH. A valanches in the area in the last 48 hours L oading by snow, wind or rain in the last 48 hours P aths, Avalanche paths T errain Traps R ating, considerable or higher on the current avalanche bulletin U nstable snow: Collapsing or cracking

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ALPTRUTH

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  1. ALPTRUTH • Avalanches in the area in the last 48 hours • Loading by snow, wind or rain in the last 48 hours • Paths, Avalanche paths • Terrain Traps • Rating, considerable or higher on the current avalanche bulletin • Unstable snow: Collapsing or cracking • Thaw instability, recent warming of the snow surface 92% of all accidents happen when 3 or more of these things are present.

  2. Avalanches ALPTRUTH • Signs of recent slides • Natural slides within the last 48 hrs • Teton Pass is closed • Debris on the roads • In www.jhsnowobs.org or on the BT report

  3. Photo Peter Thurston

  4. Photo Peter Thurston

  5. Photo Evan Howe

  6. Loading ALPTRUTH • Snow or rain in the last 48 hours • An inch an hour for 6 or more hours, making 8” total or more • Amplified by terrain features • Amplified by high winds

  7. Loading:amplified by wind From The Avalanche Handbook, McClung and Schaerer

  8. windward Leeward Safe Scary! T. Leonard Photo Loading

  9. Paths: Avalanche Paths ALPTRUTH • Large and small • Recognizable by a novice • Funnels and fans • What are the clues?

  10. Path anatomy

  11. Trim line, flag trees

  12. Terrain Traps ALPTRUTH • Often near creekbeds, roadcuts • Often not as obvoius • Consequences of being caught are amplified • “nowhere to run”

  13. Terrain Traps:Is there an escape route?

  14. Photo Don Sharaf

  15. Photo Brad Sawtell

  16. Rating: what does the avalanche report say? ALPTRUTH • www.jhavalanche.org • 307-733-2664 • Caution if it is Considerable, High, or Extreme

  17. Rating ALPTRUTH

  18. Unstable Snow ALPTRUTH • Collapsing or Whumphing • Shooting cracks • Heavy over weak

  19. Photo Don Sharaf

  20. What sound does this make when weighted?

  21. ThawInstability ALPTRUTH • Rapid temperature rise: The FIRST time the temp rises 12-15 degrees F in 12 hours or less after a long cold spell

  22. Effects of Temperature on a Slab • Cold temps = frozen and hard slab  • Rapid warming and skier triggering  • General warm temps and settlement  • Wet snow and the Melt-freeze regime

  23. Thaw Instability: rapid warming

  24. AVALANCHE TRIANGLE SNOWPACK TERRAIN WEATHER

  25. RedYellow Green LightDecision Making Don’t forget the Human Factor - Risk Tolerance -Experience -Group Size -Powder -Male Red Light Terrain -30-45 degrees -Leeward -Loaded Snowpack -Natural Avalanches -Collapsing -Shooting Cracks -Heavy over Light -Easy test scores -Q1 Shears Weather -1” an hour for 6 + hours -<12” in 24-48 hours -Wind -Rapid Warming

  26. ALPTRUTH • Avalanches in the area in the last 48 hours • Loading by snow, wind or rain in the last 48 hours • Paths, Avalanche paths • Terrain Traps • Rating, considerable or higher on the current avalanche bulletin • Unstable snow: Collapsing or cracking • Thaw instability, recent warming of the snow surface 92% of all accidents happen when 3 or more of these things are present.

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