Avalanche Forecast

Issued: Apr 2nd, 2014 9:04AM

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

triley, Avalanche Canada

South Rockies.

Summary

Confidence

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

Weather Forecast

Overnight and Thursday: Freezing level dropping to valley bottom overnight. Southwest winds developing during the day as cloud cover increases and freezing levels climb to about 2000 metresFriday: Freezing level dipping to about 1600 metres overnight and rising up to near 2000 metres during the day. Strong Westerly winds and light precipitation.Saturday: Not much drop in freezing levels overnight. Cloudy with a chance of broken skies. Light precipitation and moderate Westerly winds.

Avalanche Summary

No new avalanches reported. I suspect that loose moist or wet snow may release naturally on solar exposed terrain. Cornices have been reported to be very large and may be weakened by exposure to the strong sun of April.

Snowpack Summary

Solar radiation and high freezing levels have created new melt-freeze crusts on Southerly aspects. The 20-40cm of recent new snow sits on top of a thick sun crust on solar aspects. 70-90 cm of settling storm snow from the past week 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 140 to 170cm) 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.

Problems

Wind Slabs

Forecast new snow and Southwest wind may develop new wind slabs. Wind slabs may not bond well to the old surface. Cornices that are already weak may be easily triggered as the new snow and wind add to the load they are supporting.

Use ridges or ribs to avoid pockets of wind loaded snow.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Deep Persistent Slabs

Deep persistent weak layers have a low probability of triggering. 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

Unlikely - Possible

Expected Size

3 - 6

Valid until: Apr 3rd, 2014 2:00PM