Archived

Avalanche Forecast

Dec 11th, 2014–Dec 12th, 2014

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

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

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: Glacier.

The rain (yes rain) has stopped. Natural avalanches are less likely today but human triggering is likely. More rain is expected overnight, and danger will rise again Friday. By the weekend temperatures will drop, and the wet snowpack will tighten up.

Weather Forecast

There should be a lull in the storm today with isolated wet flurries, freezing levels to 2000m and south winds gusting to 40km/hr. Overnight, showers will bring up to 7mm of rain to 2000m. The weather pattern will be the same on Friday with showers up to 2000m. On Sat, freezing levels will finally drop to 1300m with a low of -3 and a trace of snow.

Snowpack Summary

More rain than snow fell yesterday at 1900m; 8mm of rain fell at Rogers Pass. A ~25cm storm slab, thicker in windloaded areas, will bond poorly where it overlies surface hoar or sun crust. Below 1600m it will bond poorly to a rain crust. The Nov persistent weak layers, down ~105 and ~140cm, have the potential to create large avalanches.

Avalanche Summary

Natural avalanche activity continued yesterday, with numerous size 2-2.5 avalanches occurring from all aspects and running onto avalanche fans. Avalanche debris is wet in character. The Laurie avalanche path, on the park's west boundary produced another size 3 avalanche yesterday.

Confidence

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

Avalanche Problems

Storm Slabs

A heavy storm slab that formed over the past 2 days will bond poorly to the snow below. Large natural avalanches have been occurring, running into valley bottoms. Storm slabs may step down deeper resulting in very large avalanches.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 2 - 3

Persistent Slabs

Persistent weak layers that were very reactive earlier this season are expected to wake up again with the rapid loading that is occurring. These layers are capable of wide propagations and producing very large and destructive avalanches.

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 surface hoar.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 3

Loose Wet

Rain to at least 1900m has weakened the snow. Below 1600m the wet surface snow will slide easily on buried crusts. Small sluffs may pick up snow, gaining mass. Be cautious in confined terrain features, such as gullies.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3