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Avalanche Forecast

Archived

Nov 22nd, 2016–Nov 23rd, 2016

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.

Regions

Glacier.

The Winter Permit System in now in effect (click here for more information). A series of storms may bring up to 40cm by Friday; avalanche danger is expected to increase through the week. 

Weather Forecast

Today is forecast to be mostly cloudy and dry with moderate S'ly winds at ridgetop. On Wednesday the first in a series of Pacific storms is expected. Wed expect 5cm, Thurs 20cm and Fri another 20cm! Combined with moderate to strong S'ly winds, expect new storm slabs and windslabs to develop.

Snowpack Summary

Over the past week 70cm of snow fell at 1900m and is settling into a slab. This slab sits on the November 13 crust. Recent tests on this interface indicate that in some areas the slab may bond poorly and may be triggered by skiers. Yesterday the winds increased, with S'ly winds loading lee slopes and forming pockets of windslab at ridgetop.

Avalanche Summary

Yesterday skiers reported remotely triggering a size 2 windslab in Dispatchers Bowl. The avalanche occurred from a SE aspect at 2540m. The slab was 20-40cm deep. In addition, several size 1.5 to 2.5 avalanches were triggered naturally by windloading in steep paths off Mt Macdonald and Mt Tupper. Skiers have also reported sluffing from steep slopes

Confidence

Timing, track, or intensity of incoming weather system is uncertain

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.