Avalanche Forecast Kootenay Boundary

Wednesday 6th February 2019

Avalanche Danger Ratings Wed 6th Feb 3:45PM Danger Ratings Alpine: Moderate Danger Ratings Treeline: Moderate Danger Ratings Below Treeline: Moderate Persistent Slabs Persistent Slabs Wind Slabs Wind Slabs

Avalanche Canada Forecaster: swerner

Date Issued:

Valid Until:

Persistent slab problems are not obvious and tricky to manage. This problem is mostly found in open glades and gullies at treeline and below and its just waiting for a trigger. 

Confidence

High - The weather pattern is stable on Thursday

Weather Forecast

Increasing cloud cover and light snow amounts are forecast with the incoming weather system. The weekend will remain cold.THURSDAY: Cloudy with sunny periods and isolated flurries. Alpine temperatures near -13 with light ridgetop winds from the southwest.FRIDAY: Cloudy with snow amounts 5-10 cm. Alpine temperatures near -10 and ridgetop winds moderate from the southeast. SATURDAY: Cloudy with snow amounts 5-10 cm. Alpine temperatures near -19 and ridgetop winds moderate from the East.

Avalanche Summary

On Tuesday, several skier triggered avalanches were reported. These failed on the surface hoar layer down 20-30 cm below the recent storm snow. They were easily triggered by the weight of a person on a variety of aspects from 1900-2100 m. Natural dry loose sluffing was noted from steeper terrain features. With a fairly benign weather pattern natural avalanche activity will be far and few on Thursday, however, human triggers will remain likely.

Snowpack Summary

10-30 cm of snow that fell late last week now sits on variety of snow surfaces, including buried wind crust on westerly aspects, sun crust on southerly aspects to mountain top and weak feathery surface hoar crystals in sheltered areas at treeline and below. The snowpack now hosts two predominant buried surface hoar layers. The one that was buried on February 1st seems to be more reactive to human triggers than the one buried deeper down (40-80 cm). This deeper layer of surface hoar may be most reactive below treeline on shady aspects but doesn't seem to be a widespread problem in the region. The mid-pack is generally well-settled and strong.

Persistent Slabs Persistent Slabs

Likelihood

Possible

Expected Size

1 - 2

There is a layer a layer of weak feathery surface hoar 20-40 cm below the surface and another 40-80 cm down. The former is currently reported to be most reactive, especially where it is sitting on a hard crust.

Be aware of the possibility of avalanches triggering on one layer and stepping down to anotherCaution around sheltered open areas treeline and below

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

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Wind Slabs Wind Slabs

Likelihood

Possible

Expected Size

1 - 2

Shifting winds have formed reactive wind slabs on a variety of aspects.

Watch for signs of instability like whumpfing, hollow sounds, and shooting cracks.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

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

Elevations: Alpine, Treeline.

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