Archived

Avalanche Forecast

Mar 3rd, 2017–Mar 4th, 2017

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Northwest Inland.

The CONSIDERABLE danger rating mostly reflects mountainous terrain to the West which received greater snowfall amounts and stronger winds. Backcountry areas to the East and South consider the Alpine rating to be MODERATE.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Saturday: Mostly cloudy with some sunny periods. Light winds from the SE, alpine temperatures -13 and freezing levels valley bottom.Sunday: Mostly cloudy with light winds from the SE. Alpine temperatures near-12Monday: A mix of sun and cloud with isolated flurries and light winds from the South. Alpine temperatures near -16.

Avalanche Summary

On Thursday, several natural wind slab avalanches were observed in the western part of the region on N-NW aspects in the alpine. Extensive sluffing and soft slabs were easily triggered by the weight of a skier, especially at lower elevations where the new snow sits on a firm crust. Reports from the Onion snowmobile area (Babine Mountains) indicated no recent avalanche activity. I suspect there will be little change with avalanche conditions over the weekend, however; isolated wind slabs may still be found in alpine locations on leeward slopes behind terrain features.

Snowpack Summary

Recent low density storm snow up to 25 cm has fallen with surprisingly little wind effect. The new snow has buried a variety of old snow surfaces including stiff wind slabs, facets, crusts and surface hoar. The new snow may have a poor bond to these interfaces, especially in places where the slab is stiffer and more cohesive due to winds. At treeline elevations the average snowpack depths are 120-190 cm and a well consolidated mid-pack of approximately up to 100 cm sits above weak basal facets (sugary snow) near the ground. Recent snowpack testing has shown sudden easy results down 25 cm on a surface hoar layer and sudden hard results down 100 cm within the facetted snow. The deeper basal weakness remain a concern, especially from thin rocky start zones and shallower snowpack locations.

Avalanche Problems

Wind Slabs

Gusty SW winds at upper elevations have formed fresh wind slabs on leeward slopes and behind terrain features. Loose dry avalanches may be easily triggered below treeline or in areas sheltered from the wind.

Use ridges or ribs to avoid pockets of wind loaded snow.Sheltered slopes will likely offer the best skiing today.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Deep Persistent Slabs

A lingering weakness at the bottom of the snowpack may remain sensitive to human triggering, especially in shallow snowpack areas. Smaller avalanches in motion also have the potential to step down and trigger deep persistent slabs.

Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 4