Archived

Avalanche Forecast

Mar 15th, 2014–Mar 16th, 2014

Alpine

4: High

The avalanche danger rating in the alpine will be high

Treeline

4: High

The avalanche danger rating at treeline will be high

Below Treeline

3: Considerable

The avalanche danger rating below treeline will be considerable

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

3: Considerable

The avalanche danger rating below treeline will be considerable

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: Kootenay Boundary.

Incoming weather combined with a complex snowpack means this is no time to be pushing into steep terrain. Conservative slope selection is critical to safe mountain travel.

Confidence

Fair - Intensity of incoming weather systems is uncertain on Sunday

Weather Forecast

Overview: A pacific frontal system will push inland on Saturday bringing moisture to the region until early Monday morning. Expect a ridge of high pressure to develop for Monday and Tuesday. Due to significant weather model disagreement for Sunday, I have very limited confidence in forecast snowfall amounts and freezing levels.Sunday: Moderate to heavy snowfall / Moderate westerly winds with extreme gusts / Freezing level between 1700m and 2000mMonday: A mix of sun and cloud / Moderate westerly winds becoming northwesterly with strong gusts / Freezing level at 1500mTuesday: Mainly sunny skies / Light northwest winds / Freezing level at about 1100m

Avalanche Summary

Reports from recent days include a remotely triggered deep persistent slab avalanche with a heavy trigger in a low angle meadow. The slab released on the facet/crust weakness down 80-100 cm on a NW aspect at 2100 m. I expect avalanche activity to include storm slabs with forecast weather.

Snowpack Summary

Up to 25cm of new snow overlies a fairly widespread melt-freeze crust which seems to exist on all aspects up to about 2000m. The bond between the new snow and the crust is expected to be weak, especially where surface hoar crystals (up to 8mm) sit above the crust. With more snow and wind on the way. I would expect the developing to storm slab to increase in size and reactivity.The deeper facet/crust persistent weakness buried at the beginning of February, now down 100-150 cm, is still the primary concern among most professional operators. The interface continues to show "sudden" shears in snowpack tests and has the potential to produce very large and destructive avalanches.

Avalanche Problems

Storm Slabs

Steady snowfall and wind will add to a developing storm slab problem. Expect touchy conditions, especially in wind-exposed terrain or in places where the new slab overlies buried crusts.

Be alert to conditions that change with elevation.>Choose conservative lines and watch for clues of instability.>Make observations and assess conditions continually as you travel.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4

Deep Persistent Slabs

Deep persistent weaknesses buried over a month ago continue to show reactivity in snowpack tests. Avalanches on persistent weakness are possible at all elevation bands and would be highly destructive in nature.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>Avoid convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 3 - 6

Loose Wet

Rain at lower elevations will weaken the snowpack with the potential to create pushy loose wet avalanches in steep terrain. Destructive wet slab avalanches are also possible.

Avoid steep, open glades in the forest.>Be alert to conditions that change with elevation.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 4