Avalanche Forecast

Issued: Mar 25th, 2014 9:42AM

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.

mbender, Avalanche Canada

South Rockies.

Summary

Confidence

Fair - Freezing levels are uncertain on Wednesday

Weather Forecast

Wednesday: Periods of snow possible accumulations to 5 cm. Freezing level expected 1200-1400m. Ridge winds light to moderate from the SW. Thursday: Cloudy with flurries and possible sunny breaks. Freezing level expected at 1200 m. Ridge winds light gusting to moderate from the west and southwest. Friday: Cloudy with sunny periods and isolated flurries. Light southwest ridge winds. Freezing level rising to 1900m.

Avalanche Summary

Observations from the last 4 days are limited to small loose snow avalanches on steep unsupported features.On Friday a few loose natural avalanches to size 2 were observed in steep alpine terrain. Explosive control work in the region produced size 2 avalanches that were only 10 - 30 cm in depth.

Snowpack Summary

See this great video from our South Rockies field team that does an awesome job of summarizing the current state of the snowpack.The region has picked up 60 - 100cm of storm snow that fell in the last week. Winds have been out of the SW through NW which has created fresh wind slabs in alpine and treeline 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 facet/crust persistent weakness buried at the beginning of February (now down up to 150cm) seems unlikely to trigger in areas where the hard, supportive 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 have also become large and unstable.

Problems

Storm Slabs

This problem may become more sensitive if temperatures rise as forecast through the rest of the week. Be particularly cautious in wind-loaded and cross-loaded terrain.

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

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.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Mar 26th, 2014 2:00PM