Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Mar 2nd, 2020–Mar 3rd, 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 and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
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 possible, human triggered probable.

Regions

North Columbia.

It's spicy out there right now. Between fresh wind slabs and a touchy persistent weak layer, human triggered avalanches are very likely. Keep in mind it's not always the first rider who triggers the slab.

Confidence

High -

Weather Forecast

Monday night: 5-15 cm new snow. Moderate west wind, extreme at ridgetop. Freezing level 1300 m.

Tuesday: Mostly cloudy, flurries starting in the evening. Moderate west wind. Freezing level 1300 m.

Wednesday: 10-20 cm new snow. Light to moderate west wind. Freezing level 1100 m.

Thursday: 5-10 cm new snow. Moderate southwest wind. Freezing level 1500 m.

Avalanche Summary

Friday, Saturday and Sunday saw a surge in persistent slab avalanche activity on the February 22 surface hoar layer. Numerous skier/sled triggered and remote triggered size 1-2.5 were reported by operators across the region even as professionals seek to actively avoid suspect terrain features. In a few instances, slopes were ski cut with no results, only to have the third or fourth skier in the group accidentally trigger the slab. Observations are from all aspects and elevations, but especially concentrated on north to east aspects around treeline.

Natural size 2-3.5 persistent slabs have also been observed, suspect triggers include sun, wind loading, cornice falls and tree bombs. Explosive control work Sunday produced results in the 2-2.5 range.

Snowpack Summary

Light snowfall and strong winds are building fresh wind slabs in the alpine and open areas at treeline.

A weak layer of widespread surface hoar sits 40-70 cm deep. It sits over a crust on solar aspects. The overlying snow has been cohered into slabs by incremental loading through successive storms, wind and mild temperatures. As slab character and depth increase, so do reactivity and size of avalanches failing on the weak layer. Read more about surface hoar on our forecaster blog!

The early February melt-freeze crust down 50-100 cm is dormant but still on our radar. The mid and lower snowpack is well settled and strong.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Even brief periods of direct sun could produce natural avalanches.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • The trees are not the safe-haven they normally are at this time. Terrain at treeline is primed for human triggered avalanches.
  • Surface hoar distribution is highly variable. Avoid generalizing your observations.
  • Avoid steep convex slopes.

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.

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.