Archived

Avalanche Forecast

Feb 4th, 2015–Feb 5th, 2015

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

4: High

The avalanche danger rating in the alpine will be high

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

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

Regions: Kootenay Boundary.

Avalanche danger will rise over the forecast period due loading from new snow, wind, or rain.

Confidence

Good

Weather Forecast

Freezing levels are expected to climb out of valley bottoms with the onset of snowfall on Thursday and rise above 2000 m by Friday afternoon. Precipitation is expected to arrive in three separate waves of increasing intensity over the forecast period. Expect 10-20 mm falling mostly as snow (around 15 cm) by Friday morning, then another 10-20 mm turning to rain below 2000 m throughout the day on Friday, with another 15-30 mm on Saturday. Ridge top winds are expected to peak on Friday afternoon with strong southwesterlies.

Avalanche Summary

New avalanche activity includes skier and explosive controlled wind slab avalanches up to Size 2, as well as an accidentally triggered 30cm thick persistent slab avalanche that ran on the mid-December buried surface hoar.

Snowpack Summary

Light amounts of new snow adds to the 5-20 cm sitting on a widespread hard crust that is topped by large surface hoar. This combo has been reported on all aspects and elevations, but so far weak slabs have been limited to wind-loaded slopes. The mid-January weak layer of buried surface hoar is down 25-65 cm and continues to give planar results in snow profile tests. The mid-December crust/facet/surface hoar combo found down 50 - 100cm is largely unreactive.

Avalanche Problems

Storm Slabs

New snow rests on a touchy combination of crust and surface hoar. Small sensitive wind slab and fast running sluff problems are expected to transition into thick wind slab and storm slab problems with increased loading from new snow and wind.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Be cautious of sluffing in steep terrain.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Persistent Slabs

While unlikely, you may still be able to initiate an avalanche on the mid-December crust/SH interface in isolated spots where the snowpack goes from thick to thin, especially where the crust under the new snow isn't supportive.

While unlikely, be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Carefully evaluate and use caution around thin snowpack areas.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely

Expected Size: 3 - 5