Avalanche Forecast

Issued: Mar 21st, 2014 9:35AM

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

ghelgeson, Avalanche Canada

South Rockies.

Watch the temperature and solar warming this weekend, heat and/or direct sun could quickly initiate cornice fall and natural slab avalanche activity.

Summary

Confidence

Fair

Weather Forecast

Synopsis: A ridge builds into the interior this weekend making for a fairly unexciting weather weekend. Look for high cloud, moderate freezing levels and no significant precipitation.Saturday: Freezing Level: 500m - 900m; Precipitation: Nil; Treeline Wind: Light, S | Ridgetop Wind: Moderate, WSunday: Freezing Level: 900m - 1400m; Precipitation: Trace; Treeline Wind: Light, NW | Ridgetop Wind: Moderate, NWMonday: Freezing Level: 1500m; Precipitation: Nil; Treeline Wind: Calm | Ridgetop Wind: Light, W

Avalanche Summary

On Thursday explosive control work in the region produced avalanches to size 2. A very soft slab was reportedly very sensitive to human triggering on steeper south aspects below 1800m, running on the March 19 crust.On Wednesday a size 2 wind slab was accidentally triggered by a skier in the southeast corner of the region. The avalanche occurred on a northeast aspect at about 2600m.

Snowpack Summary

15 - 50 cm of new snow has fallen in the last 48 hours accompanied by strong southwest winds which has created fresh windslabs in lee terrain. Below the new snow is a well settled storm slab which overlies a hard rain crusts. This crust exists on all aspects below 2000m and on solar aspects in the high alpine. North of Sparwood and in the Crow's Nest Pass area the buried crust seems more specific to previously sun-exposed slopes. The deep facet/crust persistent weakness buried at the beginning of February (now down up to 150cm) seems unlikely to trigger in areas where the hard, supportive near-surface crust exists. No matter where you are in the region, this weakness should stay on your radar as any activity at this interface would be large and destructive. Possible triggers include a large cornice fall, a large input in a thin snowpack area or solar warming.Cornices have also become large and unstable.

Problems

Storm Slabs

Significant snowfall and steady southwest winds have created a punchy new storm slab at all elevations. Storm slabs are likely most susceptible to human triggering on solar aspects and on wind loaded terrain features.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Choose conservative lines and watch for clues of instability.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Cornices

Cornices in the region are now very large and fragile. A cornice fall could be destructive by itself, and could trigger a large avalanche on the slope below.

Give cornices a wide berth when travelling on or below ridges.>Extra caution needed around cornices with current conditions.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 4

Deep Persistent Slabs

The deep weak layers that formed in early February may be more likely to trigger in the north of the region. Possible triggers at this point include a large cornice fall, a large force in a thin snowpack area or solar warming.

Consider the consequences of the terrain if an avalanche steps down to a persistent weakness.>Caution around convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Mar 22nd, 2014 2:00PM