Avalanche Forecast

Issued: Apr 1st, 2014 9:14AM

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 - Freezing levels are uncertain

Weather Forecast

Overnight and Wednesday: Diurnal freeze-thaw cycle with overnight freezing to valley bottoms and daytime freezing level rising to about 1600 metres. Light Northwest winds and a mix of sun and cloud. Some chance of convective flurries in the afternoon.Thursday: Diurnal freeze-thaw continues. Daytime freezing level up to about 1700 metres. Light Southwest winds during the day becoming moderate to strong by evening.Friday: Little or no overnight freeze below 1500 metres. Moderate to strong Westerly winds with a mix of sun and cloud. Chance of flurries during the day.

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

See this great video from our South Rockies field team that does an awesome job of summarizing the current state of the mid and lower snowpack.Up to 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

Southwest winds have transported the recent snow into wind slabs in the alpine and at treeline. Cornices may be weak and fall off naturally during periods of solar radiation.

Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>Cornices become weak with daytime heating, so travel early on exposed slopes.>

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.

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: Apr 2nd, 2014 2:00PM