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

Dec 28th, 2022–Dec 29th, 2022

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Purcells, Dogtooth, East Purcell.

There is a Special Public Avalanche Warning in effect for this region. Learn more: avalanche.ca/spaw

The new storm snow overlies a layer of surface hoar that is very reactive. Utilize simple terrain and careful route finding if planning mountain travel.

Deeper weak layers remain a concern for step down avalanches in wind loaded terrain.

Confidence

Moderate

Avalanche Summary

Monday and Tuesday has been very active as a skier controlled, skier accidental combined with a widespread natural avalanche cycle has occurred. This ongoing avalanche cycle produced numerous small to large (size 1-2) avalanches. These avalanche primarily failed on surface hoar that was buried in the middle of December as well stepping down to the persistent weak layer buried mid November. A number of noted avalanches reported occurred in terrain that had been previously heavily compacted, these observations and reports, support an overwhelming sense that the snowpack is currently weak, fragile and unsupportive.

Additionally, a number of these avalanches stepped down to ground as the lower snowpack is faceted weak and unconsolidated.

If you are headed into the backcountry please consider filling out a Mountain Information Network report.

Snowpack Summary

A period of warm and wet weather has moistened upper surfaces with rain reported up to the 2100m elevation.

Sustained light to moderate southwest winds have continued to move up to 40 cm of storm snow, creating wind slabs on north and east facing terrain features. Storm and wind slabs sit over hard wind affected surfaces, and a layer of facets or surface hoar that has been very active over the past 72 hrs.

The main concern is a layer of surface hoar, facets, or crusts buried 40 to 80 cm deep from mid November. Avalanche activity on this layer has tapered off but it could still be possible to trigger this layer in isolated terrain features near treeline.

Alpine snowpack distribution is variable, with depths ranging from 70 to 140 cm.

Weather Summary

Wednesday Night

Cloudy with light snowfall 1 to 2 cm. Moderate southwest winds 30 km/h. Freezing levels descending to valley bottom with alpine temperatures of -9°C.

Thursday

Cloudy some mid day clearing expected, very light snowfall, trace amounts. Light southwest winds 20 km/h. Freezing levels remain below 700 m with alpine highs of -6°C.

Friday

Clearing with no precipitation forecast. Light southwest winds 15 km/h. Freezing levels near 500 m with alpine highs of -7°C.

Saturday

Clearing with no precipitation forecast. Light southwest winds 15 km/h. Freezing levels at valley bottom with alpine highs of -12°C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Travel in alpine terrain is not recommended.

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.

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.