Avalanche Forecast

Issued: Mar 3rd, 2018 4:02PM

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

North 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

SUNDAY: Mix of sun, cloud and isolated flurries / Light to moderate southwest wind / Alpine temperature -11 MONDAY: Mix of sun, cloud and isolated flurries / Light to moderate west wind / Alpine temperature -10 TUESDAY: Mix of sun, cloud and isolated flurries / Light southwest wind / Alpine temperature -7

Avalanche Summary

Reports of avalanche activity on Thursday and Friday includes natural storm and wind slab avalanches to size 2 on north, south and west aspects from tree line into the alpine. On Friday there were two skier triggered size 2.5 persistent slab avalanche between 1800 and 1900m on south and southeast aspects. These ran on a crust buried mid-February 70cm deep. There were also a few size 1 skier triggered avalanches reported between 1400 and 2000m on Thursday. These were primarily on southerly aspects. On Wednesday a size 2 remotely triggered (from a distance of 10m) persistent slab avalanche was reported to run on surface hoar sitting on a crust that was buried mid February. This was on a southwest aspect at 1800m.

Snowpack Summary

40 to 60 cm of storm snow from the past week has been redistributed into wind slabs in wind-exposed terrain on most aspects. Below this is a layer buried mid-February that presents as a sun crust on solar aspects, and spotty surface hoar on sheltered slopes. This layer looks most concerning on on solar aspects where it's associated with with small facets or surface hoar sitting above. There are several deeper layers in the mid-pack that have shown signs of improving but remain on the radar as having a low probability of triggering yet a high consequence avalanche if they are triggered. We're 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 snowpack areas with variable snow depth and convoluted terrain.

Problems

Wind Slabs

Shifting wind means there may be old buried wind slabs in places you don't expect them (as in reverse loading).

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 2.5

Persistent Slabs

A weak layer buried up to 80cm deep "woke-up" last week. This problem seems most reactive in south-facing terrain where buried crusts exist.

Watch convoluted terrain with variable snowpack depth and multiple trigger points.Make observations and assess conditions continually as you travel.

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

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 2.5

Valid until: Mar 4th, 2018 2:00PM