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Avalanche Safety: Red Light Terrain Conditions Alert

Stay cautious of avalanches in the area with recent loading by snow, wind, or rain, visible paths, terrain traps, and high avalanche ratings. Note signs of unstable snow conditions and recent warming. Be aware of the risks and follow safety guidelines.

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Avalanche Safety: Red Light Terrain Conditions Alert

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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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