Avalanche Forecast

Issued: Feb 21st, 2017 8:00AM

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

Parks Canada percy woods, Parks Canada

Higher elevation north facing terrain is the best bet for good turns and also the area to be aware of hidden wind slab at ridgeline.

Summary

Weather Forecast

Mainly cloudy with 60% chance of flurries.  Freezing level should edge up to 1300m with an alpine high temp of -7C.  Winds are forecast to remain light from the west.  Cooling temperatures, light winds and light precipitation are forecast for  Wednesday.

Snowpack Summary

15-20cm of new snow over the last few days accompanied by generally light winds. The new snow has covered recently formed windslab at ridge-top elevations and a refrozen rain soaked surface below treeline. Layers of concern to look for are down 30-60cm and are crusts on S aspects and surface hoar on protected N facing terrain.

Avalanche Summary

Five avalanches to size 2 mainly from steep solar aspect on Mt Tupper were observed in the highway corridor yesterday. We were able to trigger a few surface slabs to size 1.0 skiing down from Avalanche Crest yesterday. The top 10-15cm were moist and would push off of convexities down the route.

Confidence

The weather pattern is stable

Problems

Wind Slabs

An icon showing Wind Slabs
Last week's strong S winds have left wind slabs at ridge top and on wind exposed terrain. The slabs appear to be bonding to the upper snowpack but may still be reactive on unsupported features. These slabs will be hidden by recent snowfall.
Be careful with wind loaded pockets while approaching and climbing ice routes.Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
Weak layers in the top meter include sun crusts on S'ly aspects and pockets of surface hoar on N'ly aspects. Field tests show isolated sudden planar results, making the weak layers hard to predict. Be careful in thin snowpack locations.
Watch for whumpfing, hollow sounds, and shooting cracks.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Feb 22nd, 2017 8:00AM