Avalanche Forecast

Issued: Apr 11th, 2019 5:57PM

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

jsmith, Avalanche Canada

Purcells.

Any appearance of the strong April sun can initiate a loose wet avalanche cycle. The likelihood of loose wet avalanches increases as temperatures warm through the day and/or if the sun comes out for a prolonged period of time.

Summary

Confidence

High -

Weather Forecast

THURSDAY NIGHT: Mostly cloudy / Light, northwesterly winds / Alpine low -4 C / Freezing level 1000 m.FRIDAY: Mix of sun and cloud / Light, southwesterly winds / Alpine high -3 C / Freezing level 1800 m.SATURDAY: Mostly cloudy with isolated flurries / Moderate, southwesterly winds / Alpine high -3 C / Freezing level 1800 m.SUNDAY: Cloudy with isolated flurries; 0-3 cm. / Light, southwesterly winds / Alpine high -5 C / Freezing level 1500 m.

Avalanche Summary

No new avalanches were reported in this region on Wednesday.On Tuesday, skiers were able to trigger slabs up to size 1.5 in steep, gully features as low as 2200m. Explosives produced avalanches to size 2 and a helicopter remotely triggered a size 1.5 avalanche from 200 m away, these avalanches all started in steep, alpine terrain above 2400 m, mostly on northerly aspects.On Sunday, small (size 1-1.5) wind slabs were reactive to skiers, generally around ridge crests and steep, convex terrain above 2200 m. The most reactive deposits were in immediate lee features, including a size 2 wind slab avalanche remotely triggered from a rocky saddle 10 m away. Overnight Sunday and into Monday, a natural avalanche cycle to size 2 occurred on the western side of the Purcells Forecast region. Storm slab avalanches to size 2, with crowns 20-50 cm deep were observed in alpine terrain on all aspects.

Snowpack Summary

5-25 cm of recent storm snow sits on a melt-freeze in most locations, except for northerly aspects above 2100 m. where the old snow surface remained dry and the recent snow sits on small surface hoar (weak, feathery crystals) in isolated locations. Southwest winds formed wind slabs in lee features below ridgetops. The depth of the snowpack deteriorates rapidly below 1200 m.Weak facets (sugary grains) remain at the bottom of the snowpack in the alpine creating a low likelihood, high consequence scenario that would likely require a large trigger to initiate an avalanche. Steep, rocky areas with a shallow or highly variable snowpack are the most likely places to trigger a very large avalanche on this layer.

Problems

Loose Wet

As temperatures rise and the snowpack warms during the day, the likelihood of loose wet avalanches will increase, especially in areas with fresh snow.

Use extra caution on slopes if the snow is moist or wet.Avoid sun exposed slopes and overhead exposure during periods of intense sun.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Wind Slabs

Recent snow has formed slabs in the alpine and alpine features around treeline. Use caution around ridge crests, lee terrain features and steep, convex slopes.

Use extra caution on slopes if the snow is moist or wet.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Apr 12th, 2019 2:00PM