Avalanche Forecast

Issued: Apr 24th, 2013 8:00AM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Loose Wet, Storm Slabs and Persistent Slabs.

Parks Canada Sylvia Forest, Parks Canada

Wide variability and springtime conditions exist.  Cornices are a prime concern for avalanche triggering.  Solar radiation is expected to be strong today, so timing and route selection will be important.

Summary

Weather Forecast

Clear skies this morning giving way to overcast skies as a weak disturbance moves through late this afternoon.  Winds may keep things cool, but direct solar radiation will cause locally very warm conditions.  Another low pressure is expected for Thursday and Friday, with cool unsettled weather for the weekend.

Snowpack Summary

In the alpine, due north aspects are maintaining dry snow conditions over multiple temperature crusts.  Solar aspects have more crusts, and daytime warming is creating sticky, wet, and/or crusty conditions.  At lower elevations (below 2200m), the snowpack is largely isothermal, but overnight re-freezing provides firm travel early in the morning.

Avalanche Summary

The number of avalanche observations is dropping off, in part due to fewer people in the backcountry to report.  Cornice failures remain the biggest concern for triggering larger slab avalanches, which are mostly failing on the April 3 PWL (sun crust-surface hoar combo), down 40-80cm.  Moist avalanches will be almost certain today.

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Friday

Problems

Loose Wet

An icon showing Loose Wet
Freezing levels may rise as high as 2000 to 2500m today, with strong solar radiation due to clear skies this morning.  Moist avalanches can be expected, especially from rocks or thin areas.  Sluff management will be a good technique today.
Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.Avoid travelling on ledges and cliffs where sluffing may have severe consequences.

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Storm Slabs

An icon showing Storm Slabs
Storm Slabs and hard wind slabs near ridge crests remain a concern.  High variability of snow depth across terrain means some areas will be quite loaded, and others very thin.  These slabs have a potential for wide propagations in the right terrain.
Be careful with wind loaded pockets. Be aware of wide variation in snowpack depthBe aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Persistent Slabs

An icon showing Persistent Slabs
Large avalanches failing on deeper weak layers are still being triggered by skiers/riders. They are also sporadically occurring naturally, triggered by wind loading, cornice fall and solar warming.
Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Be aware of the potential for full depth avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 3

Valid until: Apr 25th, 2013 8:00AM