Archived

Avalanche Forecast

Dec 18th, 2017–Dec 19th, 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

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

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

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: North Columbia.

Expect avalanche activity to increase as the recent new snow settles in the coming days.

Confidence

Low - Timing, track, or intensity of incoming weather system is uncertain on Wednesday

Weather Forecast

TUESDAY: Mainly cloudy with isolated flurries, wind light to moderate east, alpine temperature -10 WEDNESDAY: Mix of sun and cloud, wind light north, alpine temperatures -12 THURSDAY: Mix of sun cloud and isolated flurries, wind light to moderate north, alpine temperature 10

Avalanche Summary

Recent reports indicate natural and explosive triggered avalanches to size 2 and loose snow avalanches to size 1 in steep terrain. Expect to see avalanche activity increase as the new snow accumulates and settles in the coming days.

Snowpack Summary

15-30cm of new snow accumulating Friday through Sunday evening sits on a wide variety of old surfaces including large surface hoar (weak, feather-like crystals), hard crusts formed by sun or wind, and sugary facets. As the snow load builds and slab properties develop, it will be important to monitor how the new snow is bonding to the old surfaces. Most concerning would be areas that have surface hoar sitting on top of a hard crust. A crust which was formed by rain in late November is a major feature in the snowpack and is down approximately 50-80cm at tree line elevations. Snowpack tests suggest the snow above is currently bonding well to it. Snowpack depth decreases rapidly below tree line. Look out for early season hazards such as rocks, stumps, and open creeks.

Avalanche Problems

Wind Slabs

Recent west and northwest winds have created wind slabs in the lee of terrain features

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

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Storm Slabs

Expect the new snow to be become more reactive as it settles into a slab especially in sheltered areas at and below tree line where it may be sitting on a layer of feathery surface hoar crystals.

Buried surface hoar may be preserved on open slopes and convex rolls at and below tree lineWatch for whumpfing, shooting cracks, or signs of recent natural avalanches.Be cautious of sluffing in steep terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 2