Avalanche Forecast

Issued: Mar 25th, 2017 4:39PM

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

Avalanche Canada shorton, Avalanche Canada

Remember snow can lose strength very quickly on sun exposed slopes. Watch for overhead hazards and stick to supported terrain with low consequence.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

SUNDAY: Sunny in the morning then clouding over in the afternoon, light south wind, alpine temperature around -5 C.MONDAY: Cloudy with sunny periods, light southwest wind, alpine temperature around -5 C.TUESDAY: Cloudy with sunny periods, light southwest wind, alpine temperature around -5 C.

Avalanche Summary

On Friday, cornice control produced 2 cornice chunks on northeast alpine ridges. One triggered a size 1 slab and the other entrained some loose snow. A natural size 1 wind slab and cracking under skies was reported in the central part of the region. A few larger avalanches were reported midweek, including a natural size 3 avalanche on a northeast aspect at 2500 m, an explosive triggered avalanche that failed on the ground down 100 cm, and a natural size 4 deep persistent slab that failed on a broad ridge feature on south through north aspects.On Sunday, morning solar radiation is a potential trigger for cornice falls and deeper weak layers. Read the forecasters blog (here) for advice on how to manage this low probability, high consequence scenario and check out the accompanying photos (here). Also expect wind slabs in the lee of exposed terrain at higher elevations.

Snowpack Summary

10-20 cm of new snow overlies a widespread crust below around 2100 m and higher on solar aspects. Alpine wind has recently been strong mainly from south through west aspects and has loaded leeward slopes in exposed terrain at treeline and in the alpine. Large cornices are also reported in the alpine and appear to be largest on northerly aspects. At lower elevations, there are a couple rain crusts in the upper snowpack. The February crust/facet layer is now down around 90-150 cm and has been reactive with several avalanches recently releasing on it. It is expected to be most reactive in the alpine where the snowpack remains dry. The deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack and a few avalanches and cornice falls have stepped down to these layers recently resulting in very large avalanches.

Problems

Wind Slabs

An icon showing Wind Slabs
Recent wind has been from a variety of directions and wind slabs should be expected in exposed terrain on all aspects at higher elevations.
Be alert to conditions that change with elevation.Use ridges or ribs to avoid pockets of wind loaded snow.Use caution in lee areas. Recent wind loading has created wind slabs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
Sustained sun exposure or heavy triggers like a cornice falling could trigger deep, destructive avalanches on buried weak layers.
Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.Use conservative route selection, choose moderate angled and supported terrain with low consequence.If triggered, wind slabs or cornices may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Cornices

An icon showing Cornices
Cornices are large and may become weak when hit by the sun.
Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.Give cornices a wide berth when traveling on ridges.Cornices become weak with daytime heating.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Mar 26th, 2017 2:00PM