Avalanche Forecast

Issued: Apr 8th, 2016 8:55AM

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, Cornices and Wind Slabs.

rbuhler, Avalanche Canada

Northwest Coastal.

Spring conditions typically means the hazard is highest during the heat of the afternoon. Cornices and loose wet sluffing are spring problems which can be expected on Saturday. Wind slabs may also still be lingering in high elevation leeward terrain.

Summary

Weather Forecast

A mix of sun and cloud is expected for Saturday. Alpine winds are forecast to be moderate from the northwest in the morning and ease in the afternoon. Freezing levels are expected to climb to around 2200m. A mix of sun and cloud is expected for Sunday with light alpine winds and afternoon freezing levels around 2000m. Mostly cloudy conditions are forecast for Monday with light scattered flurries and afternoon freezing levels around 1500m.

Avalanche Summary

Data has become very limited for the region as we move into the spring and a lack of reported avalanche observations does not mean avalanches are not occurring. On Thursday, a natural size 3 icefall was reported north of Stewart on a south aspect at 1800m. On Wednesday, loose wet avalanches were reported on sun exposed slopes and glide cracks are reported to be moving and opening. Over the weekend, loose wet sluffing is expected on steep sun exposed slopes and cornices will become weak with daytime warming and sun exposure. Lingering wind slabs may still be reactive in exposed high elevation terrain.

Snowpack Summary

A moist or wet surface snow is being reported on all aspects at all elevations. A surface crust is expected to form Friday overnight as temperatures drop but this crust may break down during the day with warm temperatures and sun exposure. A widespread crust layer from the last period of major warming sits below the storm snow from earlier in the week. This snow is reported to be settling rapidly and generally bonding well to the crust below. Prior to the current warm conditions, strong southerly and westerly winds promoted cornice growth and formed wind slabs. These wind slabs may still be lingering in leeward terrain features at the highest elevations. A few deeply buried weak layers exist within the snowpack including a widespread crust/facet layer buried in early February down around 1.5 m and weak basal facets at the bottom of the snowpack. The near-surface crust has dramatically limited the reactivity of these destructive old layers and they have become dormant; however, they have the potential for isolated yet very large avalanches with prolonged periods of warming and solar radiation.

Problems

Loose Wet

Loose wet sluffing is likely on sun exposed slopes during the heat of the afternoon. Warm conditions may increase the size and run length of natural sluffing, and wet slabs could also be possible.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Cornices

Large cornices may become weak with afternoon warming and sun exposure. They can be destructive by themselves, and may also become the trigger for a slab avalanche on the slope below.

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

Wind Slabs

Recently formed wind slabs are expected to settle and gain strength with the warm conditions but for the short term I'd remain extra cautious of steep, wind-loaded pockets in the high alpine.

Use ridges or ribs to avoid pockets of wind loaded snow. >Be cautious as you transition into wind affected terrain. >

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 4

Valid until: Apr 9th, 2016 2:00PM