Avalanche Forecast

Issued: Apr 20th, 2014 8:58AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs, Loose Wet and Deep Persistent Slabs.

esharp, Avalanche Canada

Purcells.

At this time of year resist the urge to rely on danger ratings alone. Daytime warming or periods of sun can rapidly elevated danger ratings above what is forecast. Check out this blog post for more info on how to manage risk during the spring.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

Synopsis: A weak ridge of high pressure will shift eastwards as the next system moves in over the region Monday night with precipitation forecast for Tuesday and Wednesday.Tonight and Monday: Partly cloudy with a chance of wet flurries / Moderate southerly winds / Freezing levels 2000 - 2500m Tuesday: Flurries (5-15 cm) / Light southerly winds / Freezing levels 1900 to 2400m Wednesday: Flurries (5-20cm) / Light westerly winds / Freezing levels 1500 to 2000m

Avalanche Summary

In areas where the upper snow is moist and sits above a crust small wet slabs have been triggered by skiers. At lower elevations and on solar aspects small to large loose wet avalanche continue to be triggered on steep slopes. Cornices collapses have been reported during periods of daytime warming. Occasionally these heavy triggers have caused large deep slab avalanches on the slopes below.

Snowpack Summary

The region has recently received between 10 and 30cm of new snow with snowline currently sitting somewhere around 1100m. Below the recent snow a melt-freeze crust can be found on all but high elevation North aspects. Moderate winds have affected all Wind slabs can be found in lee features on N and E aspects in the Alpine.Several persistent weak layers still exist in the highly variable snowpack of the Purcells:-The mid-March sun crust/surface hoar layer down 50-80cm and the early-March crust/facet/surface hoar layer down around 80-120cm seem to be laying dormant for the time being.-The mid-February crust/facet/surface hoar combo is typically down 60 - 120cm. Direct triggering of this layer has become unlikely, however, cornice fall, a smaller avalanche in motion or prolonged warming may wake this layer up. The resulting avalanche would be very large and destructive.- Weak basal facets can be found in many areas, however triggering this layer is unlikely.

Problems

Wind Slabs

Moderate west winds have cause widespread wind effect in the alpine. Reactive wind slabs may be found in lee of ridges and ribs.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.>Cornices become weak with daytime heating. >

Aspects: North, North East, East, South East.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Loose Wet

Expect to see an increase in avalanche activity if the snow becomes moist with daytime warming or the sun hits cold snow for the first time.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Deep Persistent Slabs

The potential for very large deep slab avalanches needs to remain on your radar. Cornice fall, strong sun, warming temperatures or a smaller wet or wind slab avalanche in motion could act as triggers.

Be aware of the potential for very large, deep and destructive avalanches due to the presence of deeply buried persistent weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Apr 21st, 2014 2:00PM