Avalanche Forecast

Issued: Mar 22nd, 2014 10:29AM

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

ghelgeson, Avalanche Canada

South Rockies.

Check out the South Rockies Field Team's new blog. Sunny breaks on Sunday may reactivate weaknesses in the snowpack with the potential for very large avalanches.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Tuesday

Weather Forecast

Synopsis: The remnants of a very weak system pass over the region Saturday afternoon ahead of Sunday's strengthening ridge. A warm system approaches the coast Monday which should push high cloud into the region. There's potential for very high freezing levels on Tuesday, but its still too far out to say. There's a chance for significant precipitation on Wednesday.'Sunday: Freezing Level: 800m - 1200m; Precipitation: Nil; Treeline Wind: Very light, Variable | Ridgetop Wind: Moderate, NWMonday: Freezing Level: 1000m - 1200m; Precipitation: Nil; Treeline Wind: Light, NE | Ridgetop Wind: Moderate, WTuesday: Freezing Level: 1600m - 1900m; Precipitation: Nil; Treeline Wind: Moderate, W | Ridgetop Wind: Strong, W

Avalanche Summary

On Friday a few loose natural avalanches to size 2 were observed in steep alpine terrain. Explosive control work in the region produced size 2 avalanches that were only 10 - 30 cm in depth.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

See this great video from our South Rockies field team that does an awesome job of summarizing the current state of the snowpack.60 - 100 cm of storm snow fell in the last week. Winds have been out of the SW through NW which has created fresh wind slabs in lee terrain. Around 70 cm of settling storm snow rests on a graupel layer that can be found in much of the region. This makes for around 90 cm on top of the mid march crust at this point. This crust exists on all aspects below 2000m and on solar aspects in the high alpine. North of Sparwood and in the Crowsnest 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 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

Storm slabs are probably starting to settle out, but remain most most susceptible to human triggering on solar aspects and on wind loaded terrain features.

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible

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.

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

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 a bit touchier 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.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Mar 23rd, 2014 2:00PM