Avalanche Forecast

Issued: Apr 12th, 2016 8:42AM

The alpine rating is below threshold, the treeline rating is below threshold, and the below treeline rating is below threshold. Known problems include Loose Wet, Wind Slabs and Cornices.

rbuhler, Avalanche Canada

Northwest Inland.

When the sun comes out on Wednesday, expect lots of solar triggered sluffing on steep slopes. Thin new wind slabs may be reactive in leeward features in the alpine.

Summary

Weather Forecast

A mix of sun and cloud is expected for Wednesday and Thursday with light southerly winds in the alpine and afternoon freezing levels around 1500-1600m. Mainly cloudy conditions are expected for Friday with the possibility of light showers. Alpine winds are forecast to be moderate from the southwest with afternoon freezing levels around 1500m.

Avalanche Summary

On both Sunday and Monday, loose wet avalanches up to size 2.5 were reported in the far north of the region. With the arrival of spring, field observations and data have become very limited in the region. A lack of avalanche reports does not mean avalanches are not occurring. On Wednesday, newly formed wind slabs are expected to be reactive to human-triggering in the alpine. Widespread solar triggered loose sluffing is expected with the new snow sliding on the firm crust layer. Cornices have been weak recently and may fail naturally with storm loading.

Snowpack Summary

The new snowfall will bury a widespread melt-freeze crust. Strong southerly winds in the alpine will have likely formed thin wind slabs. The region should return to melt-freeze conditions on Wednesday with surface crusts forming overnight and breaking down during the day. The snowpack's strength is directly related to the thickness and strength of these surface crusts. A widespread crust/facet layer from early February and depth hoar at the bottom of the snowpack are dormant. Cycles of melting and refreezing have limited the reactivity of these old layers. However these layers, or the ground, could potentially once again be the layer for an isolated yet large avalanche with prolonged periods of warming.

Problems

Loose Wet

Loose wet sluffing is expected on steep slopes when the sun is out. The recent snowfall will be sliding on a firm crust which will likely increase the distance sluffs can travel.

Avoid steep sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet. >Be cautious of sluffing in steep terrain. >

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Wind Slabs

New snowfall and strong southerly winds likely formed thin new wind slabs in the alpine on Tuesday. These slabs will overlie a firm melt-freeze crust which may increase the slab reactivity and likelihood of triggering.

Be cautious as you transition into wind affected terrain. >Avoid freshly wind loaded features. >

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Cornices

The timing of failures is unpredictable. Unsupported sections are extra suspicious. Dropping chunks are a hazard in themselves and they may also trigger a slab avalanche on the slopes below. Watch and limit your exposure to overhead hazards.

Give cornices a wide berth when traveling on or below ridges. >Cornices become weak with daytime heating, so travel early on exposed slopes. >

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Apr 13th, 2016 2:00PM