Avalanche Forecast

Issued: Mar 5th, 2018 4:33PM

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

mbender, Avalanche Canada

South Columbia.

Recent new snow combined with wind has promoted wind slab development as well as cornice growth. As the clouds part in the coming days remember that the sun packs a punch this time of year.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

TUESDAY: Mix of sun, cloud and isolated flurries / Light southwest wind / Alpine temperature -10 WEDNESDAY: Mix of sun and cloud / Light southwest wind / Alpine temperature -9 THURSDAY: Mainly cloudy with scattered flurries / Light to moderate southwest wind / Alpine temperature -6

Avalanche Summary

Reports through the weekend highlighted numerous natural wind and storm slab avalanches size 1.5-2.5 at treeline and in the alpine on all aspects. Additionally there were also reports of skier triggered wind and storm slab avalanches to size 1.5 as well as a remotely triggered size 1.5 persistent slab avalanche on a northwest aspect at 1300m. On Sunday there was a skier triggered size 1.5 persistent slab avalanche on a southwest aspect at 2100m in the southern portion of the region. On Saturday there was a report of skier triggered size 1.5 persistent slab avalanche on a northeast aspect at 1500m with a 100cm fracture in the southern portion of the region as well.

Snowpack Summary

Storm snow total last week is 50 to 90cm and has now mostly settled. This new snow has been redistributed into localized wind slabs. It covers old surfaces including faceted powder, a sun crust on solar aspects, and surface hoar on shady slopes. Around 70 to 110cm below the surface there's a layer buried mid-February that's a sun crust on solar aspects and spotty surface hoar on sheltered slopes. This layer looks most concerning on solar aspects where it's associated with with small facets or surface hoar. There are several deeper layers that have shown signs of improving but still remain suspect as low probability to trigger yet will result as a high consequence avalanche if triggered. We are talking about surface hoar layer buried back in December and January. Near the base of the snowpack is a November crust combined with loose sugary snow. These layers may "wake-up" with strong inputs such as sustained warming, sustained snowfall, large triggers (e.g. cornice fall, smaller avalanches coming down from above); human triggering is also possible in shallow, rocky terrain.

Problems

Wind Slabs

Localized wind slabs may have formed on the down-wind side of ridges and ribs. Watch cross-loaded slopes and gullies too.

Be cautious as you transition into wind affected terrain.Extra caution needed around cornices with current conditions.Use ridges or ribs to avoid pockets of wind loaded snow.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

A weak layer buried up to 90cm deep "woke-up" last week. This problem seems most reactive in south-facing terrain where buried crusts exist.

Carefully assess and consider avoiding southerly facing slopes.Pay attention to overhead hazards like cornices which could trigger persistent slabs.Watch convoluted terrain with variable or shallow snow depths and multiple trigger points.

Aspects: North, North East, East, South East.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

1.5 - 3

Valid until: Mar 6th, 2018 2:00PM