Avalanche Forecast

Issued: Apr 11th, 2016 9:00AM

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

rbuhler, Avalanche Canada

Northwest Coastal.

A brief return to winter in the alpine for Tuesday. New snowfall and strong southerly winds are expected to form new wind slabs at higher elevations.

Summary

Weather Forecast

A weak storm system is expected to reach the coast Monday overnight. 5-15cm of snowfall is forecast with the greatest amounts along the coast. Strong southerly winds are expected in the alpine with afternoon freezing levels around 1300m. Light snowfall may continue Tuesday overnight and should be done by Wednesday morning. A mix of sun and cloud is forecast for Wednesday with light alpine wind and afternoon freezing levels around 1400m. Thursday is forecast to be mainly cloudy with sunny breaks, light alpine wind, and afternoon freezing levels around 1500m.

Avalanche Summary

On Sunday afternoon, loose wet avalanches up to size 2.5 were reported in the 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 Tuesday, new wind slabs are expected to form in the alpine. Cornices have been weak recently and may fail naturally with storm loading. Loose wet avalanches are possible at lower elevations that see rainfall.

Snowpack Summary

Dry winter snow is being reported on northern aspects above 1700m in the area north of Stewart. South aspect slopes and lower elevations are most likely undergoing daily melt-freeze cycles. Around Terrace, melt-freeze conditions are being reported at all elevations. Surface crusts are forming overnight and breaking down during the day. The snowpack's strength is directly related to the thickness and strength of these crusts. Where layers remain in the snowpack, they are generally bonding. A widespread crust/facet layer from early February and depth hoar at the bottom of the snowpack (primarily in northerly & 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

Wind Slabs

New snowfall and strong southerly winds are expected to form new wind slabs 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.

Likelihood

Possible - Likely

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

Loose Wet

Loose wet sluffing is possible on steep slopes during periods of rain. Wet slabs are also possible, especially at lower elevations.

Be cautious of wet sluffing in steep terrain. >Avoid steep slopes during periods of rain. >

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 4

Valid until: Apr 12th, 2016 2:00PM