Avalanche Forecast

Archived

Mar 1st, 2021–Mar 2nd, 2021

Alpine

Natural avalanches possible, human triggered probable.

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.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Regions

South Columbia.

Use caution as you transition into wind exposed terrain, recent fresh snow combined with strong winds have promoted wind slab development. Watch for signs of instability such as whumpfing, cracking and recent avalanches.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

MONDAY NIGHT - Mainly cloudy with a few flurries, up to 5 cm / strong southwest wind / alpine low temperature near -7

TUESDAY - Mainly cloudy with a few flurries / moderate southwest wind / alpine high temperature near -7 / freezing level 1500 m

WEDNESDAY - A mix of sun and cloud / moderate south wind / alpine high temperature near -4 / freezing level 1700 m

THURSDAY - Mainly sunny / moderate south wind / alpine high temperature near -1 / freezing level 2300 m

Avalanche Summary

Since the storm and associated avalanche cycle eased off early last week, there have been daily reports of size 1-2 natural and human-triggered avalanches in many areas. There have also been reports of larger (size 2-3) explosives triggered avalanches on most days. The size and frequency of these avalanches have generally decreased slightly each day.

There have been a few reports of sporadic persistent slab avalanches failing on the late January persistent weak layer in the past month, including one in the past week.

Snowpack Summary

There is around 60-100 cm of now sitting on a persistent weak layer of facets that was buried in mid-February. Deep wind deposits and wind slabs exist in the alpine and open treeline areas.

There is now 80-120 cm of snow above the late January persistent weak layer which is composed of surface hoar in sheltered areas in the trees and/ or a crust on steep solar aspects. Very isolated activity on this layer has been observed in the past few weeks.

Terrain and Travel

Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Be aware of highly variable recent wind loading patterns.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Be aware of the potential for large avalanches due to the presence of a persistent slab.

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.