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

Feb 28th, 2020–Feb 29th, 2020

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

Regions

Purcells.

If snowfall amounts exceed 15cm be alert for signs of instability, especially in wind affected terrain or where slab properties are building on buried surface hoar instability. Remain cautious around shallow snowpack areas, particularly if threatened by cornices. 

Confidence

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system.

Weather Forecast

FRIDAY NIGHT: Cloudy with scattered flurries, accumulation 5 to 10 cm. Winds moderate to strong southwest. Alpine low temperatures around -9 with freezing levels dropping to 800m with cold front passage.  

SATURDAY: Cloudy with scattered flurries, accumulation Trace to 5 cm. Winds moderate West gusting strong. Alpine temperature -7 C with freezing levels 1100 m.

SUNDAY: A mix of sun and cloud. Winds light Westerly. Alpine high temperatures near -8 C and lows of -12 C.

MONDAY: Cloudy with sunny periods and isolated flurries. Winds moderate West gusting strong. Alpine temperatures high of -5 and lows -10 C with freezing levels near 1000m

Avalanche Summary

A few small (size 1 to 1.5) wind and storm slab avalanches were triggered by humans each day Monday thru Wednesday with activity tapering on Thursday. They occurred on all aspects, were from 2100 to 2700m and were 15 to 40cm thick. In the Western (& deeper) portion of the region a few of the avalanches released on the surface hoar layer described in the Snowpack Summary.

Snowpack Summary

New snow and moderate strong winds are forecast to arrive Friday night into Saturday with a fast moving cold front. Total precipitations will vary from 5 to 20cm, with more snow forecast in the North and in the higher mountains of the West of the forecast region.. 

This new snow will build on the previous 10 to 30 cm of recent snow which covers a widespread layer of surface hoar (size 5 to 15 mm) that was found at all elevations and on all aspects. Recent warm temperatures have built slab like properties in this recent snow, particularly at mid and low elevations. The recent snow has been blown around by variable wind, forming wind slabs at higher elevations, particularly near ridges.  

The middle of the snowpack is strong. The base of the snowpack contains basal facets, which have been responsible for occasional and hard-to-predict Deep Persistent Slab avalanches in shallow rocky start zones.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.