Lawinenlagebericht

Yukon

Dec 27 – 28, 2021Avalanche Canada
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Lawinengefahr

Wed
Thu
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
Keine Stufe
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Kernpunkte

Small inputs of new snow will form fresh, thin but reactive wind slabs on Monday. Keep your guard up at lower elevations where hard older wind slabs may be sitting over a weak layer.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2.5

    Small inputs of new snow will form wind slabs on south through east facing slopes. Wind slabs are most reactive during their formation so watch for active wind transport for clues as to which features are being loaded. These new wind slabs are expected to bond poorly to hard, old, faceted surfaces.

    Older wind slabs may remain reactive at lower elevations where they sit over a layer of surface hoar. Keep in mind that these firm slabs can be triggered farther down slope than you might expect. Don't get surprised! 

    As you transition from sheltered areas into wind affected areas, pay attention to ski and track penetration and consider backing off if you encounter drum-like sounds or cracking. 

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2.5

    Although the crust associated with this layer has largely decomposed, the weak sugary crystals at the base of the snowpack remain. The bridging affect of the wind hammered upper snowpack is making it harder to trigger this layer but now is not the time to become complacent. When managing hard slab on top of facets, try to think in terms of consequences just in case of a surprise. "If I trigger an avalanche here, what are the consequences? Will the avalanche be large? Are there terrain traps?" 

Confidence

Moderate -

Weather Forecast

Sunday night: Around 5 cm new snow. Moderate northwest wind. Alpine temperatures -16 C.

Monday: A mix of sun and cloud. Strong northwest wind. Weak inversion with alpine temperatures around -12 C.

Tuesday: A mix of sun and cloud. Moderate northwest wind. Alpine temperatures around -12 C.

Wednesday: A mix of sun and cloud. Strong northwest wind. Alpine temperatures around -10 C.

Avalanche Summary

On Wednesday our field team observed several natural avalanches up to size 2 on Log Cabin and above Fraser Chutes. These avalanches were on cross-loaded east and south east facing slopes above treeline. 

Looking ahead, the most likely place we will see avalanche activity will be where new wind slabs are forming on south through east facing slopes.

 

Snowpack Summary

Small inputs of new snow blow over hard, wind hammered surfaces that have likely faceted in recent frigid temperatures. As a result, new wind slabs are expected to bond poorly to underlying surfaces. 

Previous winds have scoured exposed alpine and treeline areas to ground in places such as Paddy Peak and Powder Valley, with wind affected snow found well down into treeline. In the White Pass, firm wind slabs exist on south aspects and east facing gully features. Softer snow may still exist in sheltered treeline areas. 

Surface hoar may exist just below the surface at 1300m and below. It is likely only a problem where wind slab has formed above it.

The lower snowpack is made up of weak sugary snow. An avalanche at this interface is most likely to be triggered in shallow areas or with a large impact like a cornice fall or surface avalanche.

Terrain and Travel

  • Wind slabs are most reactive during their formation.
  • Keep your guard up at lower elevations. Wind slab formation has been extensive.
  • Avoid slopes that sound hollow or drum-like.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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