Avalanche Forecast

Issued: Mar 18th, 2014 9:36AM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Storm Slabs, Cornices and Deep Persistent Slabs.

jlammers, Avalanche Canada

South Rockies.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain on Wednesday

Weather Forecast

Wednesday: Light snowfall intensifying overnight (up to 10cm) / Moderate to strong westerly winds / Freezing level at 1300mThursday: Continued flurries / Moderate westerly winds / Freezing level at surfaceFriday: A mix of sun and cloud / Light northwest winds / Freezing level at surface

Avalanche Summary

In recent days avalanche observations have been very limited. There was, however, a recent report of a size 1.5 human triggered slab avalanche in the Harvey Pass area. See our Incident Report Database for more details.I expect more storm/wind slab activity in response to weather forecast for Wednesday evening.

Snowpack Summary

Up to 55cm of recent storm snow has been redistributed by strong winds into deeper deposits in lee terrain. Recent snowpack tests suggest there are still likely weaknesses near the base of the storm snow. The recent accumulations overlie hard rain crusts which exist on all aspects below 2000m and on solar aspects in the alpine. North of Sparwood and in the Crow's Nest Pass area the buried crust seems more specific to previously sun-exposed slopes. Below about 1700m rain has saturated the snowpack, and surfaces may now exist as a hard refrozen crust where temperatures have dipped below freezing.The deep facet/crust persistent weakness buried at the beginning of February, now down up to 150cm, is still producing sudden results in snowpack tests. I would be very leery of any slopes that have not already avalanched as any activity at this interface would be large and destructive. Likely triggers include a large cornice fall, a large input in a thin snowpack area or solar warming.Cornices have also become large and unstable.

Problems

Storm Slabs

Significant storm accumulations from the weekend have created fresh and reactive storm slabs which overlie fairly widespread crusts. Watch for increased triggering in wind-exposed terrain.

Be cautious as you transition into wind affected terrain.>Choose conservative lines and watch for clues of instability.>The new snow will require several days to settle and stabilize.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Cornices

Cornices in the region are now large and fragile. A cornice fall could be destructive by itself, and could trigger a large avalanche on the slope below.

Extra caution needed around cornices with current conditions.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 4

Deep Persistent Slabs

In some areas the deeply buried weak layers that formed in early February are still showing reactivity in snowpack tests. Possible triggers at this point include a large cornice fall, a large force in a thin snowpack area or solar warming.

Caution around convexities or areas with a thin or variable snowpack.>Consider the consequences of the terrain if an avalanche steps down to a persistent weakness.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Mar 19th, 2014 2:00PM