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Avalanche Forecast

Archived

Dec 22nd, 2020–Dec 23rd, 2020

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

Regions

Little Yoho.

Avalanche control Mt Whymper, Vermillion Peak and Mt. Simpson Wednesday on Hwy 93 S. No activities in these areas. Give the new load some time to adjust.

Weather Forecast

No new snow is expected over the next few days. On Wednesday NW winds will pick up in the afternoon into the strong range at 3000m. Temperatures will drop to -15C or lower in some areas Wed. AM, and alpine temperatures slightly warmer.

Snowpack Summary

A 10-15 cm over the last 24 hours which his was makes for 60+ cm over the last week in the region. The Dec 13 and Dec 7 sun crust/surface hoar/facet layers are down ~ 60cm and ~90 cm respectively. The height of snow at tree line is 80-150cm.

Avalanche Summary

Avalanche control Tuesday in Yoho  produced slides up to size 3. Many were starting as storm slabs and propagating other slabs at treeline. Further East deeper releases were seen, where upslope snow dumped over 30cm

Confidence

Due to the number and quality of field observations

Problems

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.

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.