Archived

Avalanche Forecast

Mar 20th, 2017–Mar 21st, 2017

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

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

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

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

Regions: Kootenay Boundary.

Rising freezing levels through the day on Tuesday may begin to break down the recently formed rain crust. As the crust gradually breaks down it will be important to be increasingly cautious as deeper buried weak layers may become reactive again.

Confidence

Moderate - Freezing levels are uncertain on Tuesday

Weather Forecast

TUESDAY: Cloudy with scattered wet flurries / Light to moderate east wind / Alpine temperature 2 / Freezing level 1000m rising to 2400m by late afternoonWEDNESDAY: Flurries, accumulation 5cm / Light to moderate southwest wind / Alpine temperature 1 / Freezing level 1900mTHURSDAY: Mix of sun and cloud / Light to moderate south wind / Alpine temperature -4 / Freezing level 1400m

Avalanche Summary

Since the cooling weather trend there have been no reports of significant avalanche activity. That being said reports are still rolling in about the extent of avalanche activity during the rain event. Numerous large natural avalanches including size 3 and 3.5 persistent slabs were reported throughout the region failing on deep persistent weak layers at a variety of elevations and aspects.

Snowpack Summary

Last weekend rain soaked the upper snowpack for a second time in a week. This time all the way to mountain tops. Cooling temperatures will have formed a 10-30cm rain crust on the surface. In parts of the region there may now be a thin layer of new snow sitting on top of the crust. Below the crust expect to see moist or wet snow. The late-February facet / surface hoar interface (70-120 cm deep), the mid-February crust (90-130 cm deep), and basal facets in shallow snowpack areas may still be present at upper elevations and may still be reactive and become a concern as surface crusts break down with daytime warming.

Avalanche Problems

Loose Wet

As the freezing level rises the surface snow will become increasingly wet or moist and may begin to sluff from steep terrain.

Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.If triggered smaller avalanches may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1 - 2

Persistent Slabs

The likelihood of triggering persistent slabs has decreased substantially at lower elevations. At upper elevations where the recent rain crust is not as thick and strong, there is still potential to trigger deeper buried weak layers.

Be alert to conditions that change with elevation.Be aware of thin areas that may propogate to deeper instabilites.Pay attention to overhead hazards like cornices which could easily trigger deep slabs.

Aspects: All aspects.

Elevations: Alpine.

Likelihood: Unlikely - Possible

Expected Size: 2 - 3