Avalanche Forecast

Issued: Apr 13th, 2016 8:35AM

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 Coastal.

Spring problems including loose sluffing and cornice failures are the main concern when the sun is out on Thursday. Lingering wind slabs may still be reactive in leeward features in the alpine.

Summary

Weather Forecast

Mostly sunny conditions are expected for Thursday with light southerly winds in the alpine and afternoon freezing levels around 1500m.Â Snowfall is expected to start Thursday night and 10-15cm is expected by Friday evening.Â Moderate to strong southerly winds are forecast for Friday with freezing levels around 1300m.Â Another 10-20cm is forecast for Saturday with moderate to strong southerly winds and 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 quite limited in the region. A lack of avalanche reports does not mean avalanches are not occurring. On Thursday, recently formed wind slabs may still be reactive to human-triggering in the alpine. Solar triggered loose sluffing is possible, especially in places that didn't see sun on Wednesday. Lingering cornices will become weak with afternoon warming and sun exposure.

Snowpack Summary

5-15cm of new snow fell at higher elevations on Tuesday. Strong southerly winds redistributed this snow in exposed alpine terrain and likely formed wind slabs in leeward features. The new snow has buried a widespread melt-freeze crust. With the exception of high elevation shaded terrain, the region has likely returned to melt-freeze conditions on Wednesday with surface melting during during the day and crust formation overnight. 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 (primarily in northern & inland areas) 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 should be 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.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Wind Slabs

Recently formed wind slabs may still be reactive to human-triggering in leeward alpine terrain. These slabs likely overlie a firm melt-freeze crust which may increase the slab reactivity and likelihood of triggering.

Use caution in lee areas in the alpine. Recent wind loading have created wind slabs. >Use ridges or ribs to avoid pockets of wind loaded snow. >

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

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.

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

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Apr 14th, 2016 2:00PM