Avalanche Forecast

Issued: Apr 3rd, 2017 4:40PM

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

rbuhler, Avalanche Canada

Kootenay Boundary.

Recently formed wind slabs on high elevation north aspects may remain reactive to triggering on Tuesday. Extra caution is needed around all steep sun exposed slopes as well any slopes exposed to large cornices during the heat of the day.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

Mostly sunny conditions are expected Tuesday morning with a mix of sun and cloud in the afternoon. Alpine wind is expected to be light to moderate from the southwest. Freezing levels are expected to fall to valley bottom on Monday night and reach around 1700 m on Tuesday afternoon. Mostly cloudy conditions are expected on Wednesday with light snowfall beginning in the afternoon or evening. Alpine wind is expected to be moderate to strong from the southwest and freezing levels are forecast to reach around 2000 m. 5-10 cm is currently forecast for Wednesday night. A break between storm pulses is expected for Thursday with the next system arriving Thursday evening.

Avalanche Summary

On Sunday, natural sluffing was reported from very steep terrain. Ski cutting was triggering size 1 sluffs with the recent storm snow sliding on a crust. On Saturday, isolated natural storm slab avalanches were reported with thickness of 20 cm. Natural sluffing was also reported on all aspects. On Tuesday, the main concern is lingering wind slabs in high elevation north facing terrain and loose wet avalanche from steep sun exposed slopes. Cornices are expected to become weak with daytime warming and sustained sun exposure.

Snowpack Summary

The region is expected to have entered a period of widespread melt-freeze conditions on all aspects and elevations except for high north facing terrain where the surface snow is expected to remain dry. In high elevation terrain, recent strong southwest winds and new snowfall has formed wind slabs in leeward features. At lower elevations and on sun exposed slopes, there are likely several well bonded crust layers in the upper snowpack. A rain crust which was buried on March 21 extends into the alpine is now down 60-80 cm. This crust was the bed surface for several avalanches during the solar cycle at the end of last week. At elevations above around 2100m, the February persistent weak layers may still be lingering down around 100-150cm and weak basal facets may still be lingering in shallow snowpack areas. These deep weak layers appear to have gone dormant but an isolated avalanche or cornice fall still has the potential to step down in the right conditions.

Problems

Wind Slabs

Wind slabs have recently formed in north facing terrain at higher elevations and are expected to remain reactive to human triggering on Tuesday.

Be alert to conditions that change with elevation.Use caution on steep open slopes and unsupported convex rollsUse ridges or ribs to avoid pockets of wind loaded snow.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Cornices

Large cornices are expected to become weak with daytime warming and sustained sun exposure.

Give cornices a wide berth when travelling on or below ridges.Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.Pay attention to overhead hazards like cornices which could trigger a deep persistent slab.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Loose Wet

Solar triggered loose wet avalanches should be expected from steep sun exposed slopes during the heat of the day.

Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Be cautious of sluffing in steep terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Apr 4th, 2017 2:00PM