Archived

Avalanche Forecast

Mar 8th, 2019–Mar 9th, 2019

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

1: Low

The avalanche danger rating at treeline will be low

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

1: Low

The avalanche danger rating in the alpine will be low

Treeline

1: Low

The avalanche danger rating at treeline will be low

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: South Columbia.

Storm slabs may be reactive to human triggering, especially in wind loaded areas, and at upper elevations. Watch for signs of instability such as whumphing, cracking and recent avalanches.

Confidence

Moderate -

Weather Forecast

FRIDAY NIGHT - Mainly cloudy with clear periods / northwest winds, 10 km/h / alpine low temperature near -12SATURDAY - A mix of sun and cloud / northwest winds 10 km/h / alpine high temperature near -11SUNDAY - Mainly sunny / northwest winds 10-15 km/h / alpine high temperature near -9MONDAY - Flurries, 5-10 cm / south winds 20-40 km/h / alpine high temperature near -6

Avalanche Summary

On Friday, there were preliminary reports of a natural wind slab avalanche cycle to size 2.5 in the neighboring Glacier National Park region.On Thursday, there were several reports of human triggered wind slab, storm slab and loose snow avalanches, size 1-1.5, and natural loose and storm slab avalanches up to size 2.5.On Wednesday, a size 2 persistent slab avalanche was triggered by a cornice failure on a southeast aspect in the alpine. This avalanche reportedly failed on the late-January persistent weak layer.Persistent slab avalanche activity on the buried surface hoar layers (described in more detail in the Snowpack Summary) has tapered significantly. This has evolved into a low likelihood avalanche/high consequence avalanche problem at treeline and below.

Snowpack Summary

15-35 cm of recent storm snow is sitting mainly on wind slabs and facets (sugary snow), as well as surface hoar (feathery crystals) in sheltered areas and a crust on sun exposed slopes. There are two weak layers of surface hoar in the upper snowpack that were buried in late January and early February. They can be found between 40-90 cm below the surface. These layers consist primarily of surface hoar, though they may be associated with crusts on steeper, south facing slopes. These weak layers are most prominent at lower elevations, especially below treeline. The lower snowpack is generally considered to be strong, except for shallow, rocky areas where the cold temperatures continue to facet (weaken) the snowpack.

Avalanche Problems

Storm Slabs

Fresh storm slabs may be reactive, especially in wind loaded areas.

Avoid wind loaded pockets near ridge crests and back off from slopes that feel hollow or drum-like.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 1.5

Persistent Slabs

Two surface hoar layers are buried between 40-90 cm. Avalanche occurrences on these layers have become infrequent, however it may still be possible to trigger an avalanche in isolated locations such as steep cutblocks and large open glades.

Exercise increased caution around low elevation cut-blocks where this layer has been well preserved.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood: Unlikely

Expected Size: 1 - 2