Avalanche Forecast

Issued: Apr 11th, 2017 3:54PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Cornices and Wind Slabs.

Avalanche Canada mgrist, Avalanche Canada

Significant uncertainty surrounds snowfall amounts on Wednesday-Thursday. If you see more than 25cm fresh snow, danger ratings will be CONSIDERABLE. Limit your exposure to cornices when it's cloudy and completely avoid them when it's sunny.

Summary

Confidence

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

Weather Forecast

There's significant uncertainty surrounding precipitation on Wednesday-Thursday (wide range given), and then some clearing for Friday. WEDNESDAY: Flurries late morning into the afternoon (5-10cm). Moderate southerly ridgetop winds. Freezing level around 1700 m.THURSDAY: Snow continues Wednesday overnight with 5-20cm possible by Thursday afternoon. Moderate southwest ridgetop winds. Freezing level around 1900 m.FRIDAY: Clearing Thursday overnight and then cloudy by Friday afternoon. Strong southwest ridgetop winds. Freezing level around 1800 m.

Avalanche Summary

On Tuesday, skiers were able to trigger a 20cm deep Size 1.5 wind slab on an east aspect near Fernie. On Monday, several storm slabs and cornice triggered slabs to Size 2.0 were reported on northerly aspects between 1750m and 2100m.Some small, loose wet avalanches to Size 1.5 were reported on south facing aspects near 1750m in the afternoon on Monday.

Snowpack Summary

Since Saturday morning, 15-30 cm of new snow has fallen at treeline and above. The sun on Monday & Tuesday made snow surfaces moist and unstable during the day, but it should stabilize quickly after an overnight refreeze. This new snow sits on a very hard crust up to 1400m (on north aspects) and up to 1700m (on south aspects).Moderate southwesterly winds have created wind slabs on lee features below alpine ridgetops. Cornices are large, looming, and best avoided.The snowpack is generally well settled and continues to transition into a spring snowpack, becoming isothermal at treeline in some areas and below treeline in most areas.The December facets and November rain crust are buried deep, but these deep persistent weaknesses have not been reactive for several weeks. That said, rapid warming of the snowpack or a large trigger, like a cornice, could trigger this layer.

Problems

Cornices

An icon showing Cornices
Solar radiation and daytime warming are common cornice triggers. Limit your exposure when it's cloudy and completely avoid cornices when it's sunny.
Cornices become weak with daytime heating, so travel early on exposed slopes.Give cornices a wide berth when travelling on or below ridges.Minimize exposure to overhead hazard from cornices.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Wind Slabs

An icon showing Wind Slabs
New snow and moderate southwest winds have formed wind slabs below alpine ridgetops.
Use ridges or ribs to avoid pockets of wind loaded snow.Be alert to conditions that change with elevation.Approach steep lee and cross-loaded slopes with caution.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Apr 12th, 2017 2:00PM

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