Avalanche Forecast

Issued: Feb 28th, 2018 5:06PM

The alpine rating is considerable, the treeline rating is moderate, 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 beginning late Thursday and 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

A strong southeast flow system will bring snowfall beginning late Thursday afternoon.Â Amounts are uncertain but accumulations of more than 15 cm by Friday morning may be possible in some areas.TONIGHT: Flurries. Accumulation trace. Ridge wind moderate, southwest. Temperature near -9. Freezing level lowering to valley bottom.THURSDAY: Snow increasing in the afternoon and overnight. Accumulation 10-15 cm. Ridge wind light to moderate, southeast. Temperature near 0. Freezing level rising to 1400 m.FRIDAY: Mainly cloudy, flurries increasing overnight. Accumulation 2-10 cm. Ridge wind light, east. Temperature near -4. Freezing level 600 m.SATURDAY: Mainly cloudy, light flurries. Accumulation trace. Ridge wind light, northeast. Temperature near -5. Freezing level 600 m.

Avalanche Summary

There have been no new avalanches reported since Monday when 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 were reported.

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

Storm Slabs

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

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

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 deep slabs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3.5

Valid until: Mar 1st, 2018 2:00PM