Avalanche Forecast

Issued: Apr 8th, 2014 10:35AM

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

ghelgeson, Avalanche Canada

Purcells.

Summary

Confidence

Fair

Weather Forecast

Synopsis: A weak ridge lingering in the wake of the cold front should result in mostly dry weather Wednesday and Thursday before it breaks down Thursday night. Looks like an organized low pressure system could move into the interior Friday bringing light to moderate precipitation.Tuesday Night: Freezing Level: 2000m lowering to 1200m; Precipitation: 4:6mm - 4:10cm;Wednesday: Freezing Level: 1500m - 1600m; Precipitation: Trace; Wind: Treeline: Light, W | Ridgetop: Moderate, WThursday: Freezing Level: 1200m rising to 2200m; Precipitation: Nil; Wind: Treeline: Light, W | Ridgetop: Moderate, WFriday: Freezing Level: 1500m - 2000m; Precipitation: Trace; Wind: Treeline: Moderate, SW | Ridgetop: Moderate, W

Avalanche Summary

A couple size 1 avalanches with crowns 15 - 30 cm deep were triggered by skiers on a NE facing feature around 2300m in the central Purcells Monday. Some pinwheeling/snowballing was observed from steep terrain in the northern Purcells. No other significant activity to report.

Snowpack Summary

Warm temperatures resulted in the freezing level reaching to almost 2400m early this week in the southern Purcells, around 1800m in the north. This has helped to settle out last weeks storm snow, it's reported to be bonding well to the old surface. Strong winds out of both the SW and NW have redistributed what little dry snow still exists at upper treeline and alpine elevations into wind slabs that are most prevalent immediately lee of ridge crest Three persistent weak layers exist in the highly variable snowpack of the Purcells:The mid-March sun crust/surface hoar layer down 50-80cm still has potential for human-triggering in isolated areas. The early-March crust/facet/surface hoar layer down around 80-120cm has become less susceptible to human triggering, but still has the capacity to produce large avalanches.The mid-February crust/facet/surface hoar combo is typically down 60 - 120cm. Direct triggering of this layer has become unlikely, however, cornice fall, a smaller avalanche in motion or prolonged warming may wake this layer up, which would result in very large and destructive avalanches.Weak basal facets exist in many areas, but triggering is unlikely.

Problems

Wind Slabs

Wind slabs immediately lee of ridge crest and mid slope features may still be sensitive to human triggering. Keep an eye on overhead cornices too, you don't want to be underneath or on top of one when it releases.

Give cornices a wide berth when travelling on or below ridges.>Be careful with wind loaded pockets, especially near ridge crests and roll-overs.>Carefully evaluate big terrain features by digging and testing on adjacent, safe slopes.>Assess start zones carefully and use safe travel techniques.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Deep Persistent Slabs

A bomber spring snowpack is still a few weeks away. For now, the potential for very large deep slab avalanches needs to remain on your radar. Cornice fall, strong solar, warming temps or a surface avalanche in motion could wake the sleeping giant.

Carefully evaluate big terrain features by digging and testing on adjacent, safe slopes.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Be aware of the potential for very large, deep and destructive avalanches due to the presence of deeply buried persistent weak layers.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

4 - 8

Valid until: Apr 9th, 2014 2:00PM