Avalanche Forecast

Issued: Mar 1st, 2018 4:45PM

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

jmcbride, Avalanche Canada

South Rockies.

A strong southeast flow is expected to bring more snow Thursday night into Friday. Amounts are uncertain but expect to find new storm slabs building especially at upper elevations.

Summary

Confidence

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

Weather Forecast

TONIGHT: Snow. Accumulation 5-15. Ridge wind moderate, east. Temperature near -8. Freezing level lowering to valley bottom.FRIDAY: Cloudy, snow. Accumulation 5-15 cm. Ridge wind light, northeast. Temperature near -4. Freezing level 600 m.SATURDAY: Mainly cloudy, light flurries. Accumulation 2-5 cm. Ridge wind light, northeast. Temperature near -6. Freezing level 600 m.SUNDAY: Mix of sun and cloud. Ridge wind light, west. Temperature near -6. Freezing level 500 m.

Avalanche Summary

Over the past week there have been 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 that were reported on Monday.Last weekend there were two reports of snowmobilers triggering a size 1.5 and size 2 wind slab releases on northeast to east aspects between 2000-2100 m in the Window mountain area.

Snowpack Summary

About 15-30 cm of new snow now covers previously wind-scoured, westerly slopes and old hard and soft wind slabs on leeward, easterly alpine and treeline slopes. Beneath these old wind slabs lies a well-settled mid-pack. 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

Storm Slabs

New snow and wind may form touch storm slabs particularly on lee and cross-loaded slopes at and above treeline.

Be cautious as you transition into wind affected terrain.If triggered, the wind slabs may step down to deeper layers, resulting in large avalanchesWatch for signs of instability such as whumpfing, or cracking.

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.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3.5

Valid until: Mar 2nd, 2018 2:00PM