Avalanche Forecast

Issued: Mar 24th, 2014 8:40AM

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

Peter, Avalanche Canada

South Rockies.

Summary

Confidence

Fair - Freezing levels are uncertain on Tuesday

Weather Forecast

Tuesday: Mainly cloudy with possible showers or flurries. The freezing level should climb to around 2000 m (or a little higher). Ridge winds are light to moderate from the SW. Wednesday: Periods of snow 10-20 cm. The freezing level is around 1000-1200 m and ridge winds are light to moderate from the SW. Thursday: Cloudy with flurries. The freezing level is around 1200 m and ridge winds are light.

Avalanche Summary

Recent activity has been limited to loose dry or loose wet sluffing in steep terrain and a few skier and explosive controlled slab avalanches up to size 2. These recent slabs only involved the storm snow and were around 20-30 cm deep on average.

Snowpack Summary

The region picked up 5 - 10cm of convective snowfall Saturday night which adds to the 60 - 100 cm of storm snow fell in the last week. Winds have been out of the SW through NW which has created fresh wind slabs in lee terrain. Around 70 cm of settling storm snow rests on a graupel layer that can be found in much of the region. This makes for around 90 cm on top of the mid march crust at this point. This crust exists on all aspects below 2000m and on solar aspects in the high alpine. North of Sparwood and in the Crowsnest Pass area, the buried crust seems more specific to previously sun-exposed slopes. The deep mid-February facet/crust persistent weakness, now down up to 150cm, seems unlikely to trigger in areas where the hard, supportive crust exists. No matter where you are in the region, this weakness should stay on your radar as any activity at this interface would be large and destructive. Possible triggers include a large cornice fall, a large input in a thin snowpack area or solar warming. Cornices are also large and unstable.See this great video from our South Rockies field team that does an awesome job of summarizing the current state of the snowpack.

Problems

Storm Slabs

This problem may become more sensitive if temperatures rise as forecast on Tuesday. Be particularly cautious in wind-loaded and cross-loaded terrain.

Be cautious as you transition into wind affected terrain.>Choose conservative lines and watch for clues of instability.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Cornices

Cornices in the region are now very 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, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Deep Persistent Slabs

The deep weak layers that formed in early February may be a bit touchier in the north of the region. Possible triggers at this point include a large cornice fall, surface avalanche in motion 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

Possible

Expected Size

3 - 6

Valid until: Mar 25th, 2014 2:00PM