Avalanche Forecast

Issued: Apr 13th, 2019 4:23PM

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

jsmith, Avalanche Canada

Purcells.

Lingering wind slabs may still be reactive to human triggers in isolated locations, such as steep, north facing slopes below alpine ridgetops.

Summary

Confidence

High -

Weather Forecast

SATURDAY NIGHT: Cloudy with flurries; 0-3 cm. / Moderate, southwesterly winds / Alpine low -5 C / Freezing level 1200 m.SUNDAY: Mix of sun and cloud with isolated flurries; 0-3 cm. / Light, westerly winds / Alpine high -2 C / Freezing level 1600 m.MONDAY: Mix of sun and cloud / Light, southwesterly winds / Alpine high -2 C / Freezing level 1600 m.TUESDAY: Mostly sunny / Light, westerly winds / Alpine high 0 C / Freezing level 1800 m.

Avalanche Summary

On Friday, explosive cornice control work dropped a large cornice on a rocky slope which triggered a size 2.5 slab avalanche 50 cm deep on a northeast aspect.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. They initiated in steep, alpine terrain above 2400 m, mostly on northerly aspects.

Snowpack Summary

Currently, the snowpack structure changes dramatically with elevation and aspect. 5-25 cm. of recent storm snow (amounts tapering with elevation) is sitting on a melt/freeze crust, except for north facing terrain above 2100 m. where the old snow surface remained dry and small surface hoar (weak, feathery crystals) may be present in isolated locations. This recent snow has been affected by the sun and re-distributed by southwesterly winds, forming wind slabs on lee features below ridgetops.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.Below roughly 1900 m, the snowpack is moist and is melting rapidly at lower elevations. Check out this useful link for managing avalanche hazard during spring conditions HERE.

Problems

Wind Slabs

Lingering wind slabs may still be reactive to human triggers; especially in lee features below ridgetops.

Pay attention to changing conditions with elevation/aspect.Avoid wind loaded slopes below ridgetops.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Loose Wet

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.

Avoid sun exposed slopes when the solar radiation is strong, especially if the snow is moist or wet.Avoid terrain traps such as cliffs and gullies that increase the consequence of small avalanches.Cornices become weak with daytime heating, travel early on exposed slopes.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Apr 14th, 2019 2:00PM