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Avalanche Forecast

Archived

Jan 6th, 2021–Jan 7th, 2021

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

Regions

Glacier.

Human-triggering of storm slabs is being reported throughout the park. All incidents seem to be from areas where slightly more wind has tightened the surface. Watch for whumphing/cracking of the snow surface for clues of instability.

Weather Forecast

One last pulse of snowfall today, then a dry period for a few days.

Today: flurries, 5-10cm, alpine high -5*C, mod SW winds

Tonight: cloudy, alpine high -9*C, light S winds

Thurs: cloud with sunny periods, alpine high -4*C, light S winds

Fri: sun and cloud, alpine high -1*C, light S winds

Snowpack Summary

In the past 4 days, 90cm of snow, SW winds, and mild temps have created a surface storm slab. This sits on a surface hoar layer, buried Dec 26, which is preserved in sheltered areas at and below treeline. The Dec 13 surface hoar can still be found down 120cm and the Dec 7 crust/facet/surface hoar (aspect/elevation dependent) layer is down 135+cm.

Avalanche Summary

Human-triggered activity seems to be confined to areas at and below treeline that have had wind to create a reactive surface slab. A sz 2 skier accidental on the east end of the park was reported on the MIN, while more activity was observed in Puff Daddy and Napoleon Spur on Monday.

Natural activity overnight on Macdonald and Tupper to sz 2.5.

Confidence

Intensity of incoming weather systems is uncertain

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.