Archived

Avalanche Forecast

Jan 31st, 2018–Feb 1st, 2018

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

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: Northwest Inland.

Be extra cautious around convexities where wind slabs and persistent slabs are easiest to trigger.

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Saturday

Weather Forecast

THURSDAY: Isolated flurries / light to moderate southwest wind / alpine temperatures around -10 C.FRIDAY: Flurries with accumulations of 5-10 cm / moderate west wind / alpine temperatures around -12 C.SATURDAY: Flurries with accumulations of 5-15 cm / moderate west wind / alpine temperatures around -10 C.

Avalanche Summary

On Tuesday, a small storm slab (size 1.5) was triggered by a skier on a southwest aspect at 1250 m. Natural activity was also likely during the storm. Otherwise, most of the recent reported activity has been loose dry snow sluffing in steep terrain. Some persistent slab activity has been reported over the past few days as well. A large naturally-triggered size 3 slab avalanche was reported on an east aspect at 1900 m in the Howsons on Monday, and two large remotely triggered avalanches (size 2.5) were reported late last week on north at west aspects around 1600 m north of Kispiox. The December weak layer was the suspected failure plane.

Snowpack Summary

Strong winds have built wind slabs in exposed terrain. 30-60 cm of snow lies over a crust and/or weak feathery surface hoar layer buried in mid-January. The crust exists well into the alpine and the surface hoar can be found in sheltered areas in the lower alpine and treeline elevations. Another two crust / surface hoar layers that formed in December are buried 50-80 cm below the surface. These layers produced sudden results in recent snowpack tests and have been the suspected weak layer in recent large remotely (from a distance) triggered avalanches.

Avalanche Problems

Wind Slabs

Wind slabs can be found on lee aspects in the alpine and wind-exposed areas at treeline. Wind slabs are sitting above a thin crust or a layer of surface hoar.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 1.5

Persistent Slabs

Weak layers buried 30-80 cm below the surface have produced some recent avalanches, particularly on unsupported features.

Watch for signs of instability such as whumpfing, or cracking at lower elevations.Avoid shallow or thick to thin snowpack areas where triggering a deeper layer is more likely.Evaluate unsupported slopes critically.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 1.5 - 3