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Avalanche Forecast

Archived

Jan 16th, 2022–Jan 17th, 2022

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

Regions

Lizard-Flathead.

Strong wind will continue blowing. Expect wind-loaded pockets around ridge crest in upper elevations. 

Confidence

High - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

SUNDAY NIGHT: Partially cloudy, strong west wind, treeline low around -5 C, freezing level around 1000 m.

MONDAY: Snow late afternoon 5 cm, treeline high around -3 C, strong southwest wind, freezing level around 1500 m.

TUESDAY: Snow, 5 cm, light variable winds, treeline high around -10 C, freezing level returning to valley bottom.

WEDNESDAY: Clearing, light southwest winds, treeline high around -12 C, freezing level returning to valley bottom.

Avalanche Summary

No new avalanches were observed nor reported in the last 24 hours.

Thursday, three very large avalanches were reported from this region. The avalanches appear to have failed on the early December crust and showed wide propagation. They occurred on southwest to southeast aspects and were naturally triggered in response to rising temperatures and solar radiation.These avalanches follow a previous sporadic pattern of very large avalanches that have been reported from this region and neighbouring regions over the last couple of weeks. 

Snowpack Summary

Fresh dry snow can still remain at upper elevation but will be most likely wind affected. Around 2000 m and below, a crust is now capping the dense 15 cm of snow which has settled significantly with the past mild temperatures. The crust varies from thin/breakable to thick/supportive, according to the aspects and elevation. Under it, the snowpack consists of a variety of old surfaces, including soft snow in sheltered areas and wind slabs in exposed and open areas, which formed over the past few days.

The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 100-270 cm. This layer appeared to have "waken up" in response to warm temperatures and solar radiation on Thursday Jan 13, when at least three very large avalanches were reported on this layer. This layer has created a low likelihood, high consequence scenario which is best managed through conservative terrain choices and disciplined backcountry travel techniques.

Terrain and Travel

  • Wind slabs may be poorly bonded to the underlying crust.
  • Be alert to conditions that change with elevation and wind exposure.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • 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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.