Avalanche Forecast

Issued: Feb 27th, 2018 4:56PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Wind Slabs and Deep Persistent Slabs.

jmcbride, Avalanche Canada

South Rockies.

Strong winds are forming wind slabs in leeward areas at upper elevations. Avoid pillows of stiff or chalky looking snow, and be wary of lingering under overhead hazards such as cornices which may be large and fragile.

Summary

Confidence

Weather Forecast

TONIGHT: Flurries. Accumulation trace. Ridge wind moderate to strong, west. Temperature near -10. Freezing level lowering to valley bottom.WEDNESDAY: Mix of sun and cloud, light flurries. Accumulation trace. Ridge wind moderate, southwest. Temperature near -4. Freezing level rising to 1000 m.THURSDAY & FRIDAY: Mostly cloudy, flurries heaviest overnight Thursday. Accumulation up to 5 cm. Ridge wind moderate, southeast easing on Friday. Temperature high near 0, low near -8. Freezing level rising to 1500 m on Thursday.

Avalanche Summary

Monday there were reports of both natural and skier triggered loose dry avalanches in steep terrain, as well as skier and explosive triggered storm slab avalanches up to size 1.

Snowpack Summary

Strong to extreme winds have scoured windward slopes and formed cornices and hard and soft wind slabs on (downwind) alpine and treeline slopes. These wind slabs overlie various surfaces, including older hard wind slabs, crusts, facets and spotty surface hoar.The lower snowpack is weak with two primary concerns that are generally widespread:1) A widespread weak layer from mid-December composed of facets, crusts, and surface hoar that is 100-150 cm deep.2) A rain crust with sugary facets buried in late November near the bottom of the snowpack.

Problems

Wind Slabs

Touchy wind slabs may be found on a variety of lee and cross-loaded slopes at and above treeline.

Avoid steep slopes below cornices.Be cautious as you transition into wind affected terrain.If triggered, the wind slabs may step down to deeper layers, resulting in large avalanches

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

Deeply buried weak layers are most likely to be triggered from thin or variable snowpack areas; or with a large load, like a cornice fall.

Pay attention to overhead hazards like cornices which could easily trigger deep slabs.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3.5

Valid until: Feb 28th, 2018 2:00PM