Avalanche Forecast

Issued: Feb 15th, 2017 4:48PM

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

cam_c, Avalanche Canada

Purcells.

Watch for conditions that change with elevation. Heavy rain at lower elevations means heavy snow up high.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

THURSDAY: 5-10 mm of precipitation with moderate southwesterly winds and freezing levels around 2000 m.FRIDAY: Unsettled conditions with isolated flurries, moderate becoming light southwesterly winds and freezing levels dropping to 1500 m.SATURDAY: A mix of sun and cloud with flurries possible late in the day, light winds and freezing levels around 1300 m.

Avalanche Summary

Reports from Tuesday include continued natural loose wet avalanche activity up to size 1.5 on steep sun exposed slopes, as well as a 70 cm deep by 200 m wide Size 3.5 natural storm slab avalanche that ran 1000 m from a south facing alpine start zone. On Sunday, explosives triggered numerous storm slabs up to size 2.5 as well as two deep persistent slabs up to size 3.5 which released down 200 cm, most likely on the November crust. Rain at lower elevations is expected to destabilize the upper snowpack resulting loose wet sluffing and potentially increasing the sensitivity of triggering persistent slab avalanches. In the alpine, touchy new wind slabs have the potential to step down and trigger persistent slab avalanches.

Snowpack Summary

Flurries have resulted in light amounts of fresh snow at higher elevations, while elsewhere the snow surface has become wet, loose and cohesionless on sun-exposed slopes and at lower elevations. Rapidly settling storm snow from last week is still bonding poorly to the previous snow surface from early February, which is now down 60-80 cm and includes a sun crust on steep sun-exposed slopes, faceted snow, as well as surface hoar on sheltered open slopes. Recent strong winds from the south and west had redistributed the recent storm snow in exposed terrain forming wind slabs. A persistent weakness buried mid January is now down 80-150 cm and the November crust is down around 200 cm. These deep persistent weaknesses appear to be waking up with the warmer temperatures and several avalanches have recently released up to 2 m deep.

Problems

Persistent Slabs

A persistent weakness down 60-80 cm remains remains sensitive to light triggers in isolated areas. Smaller avalanches have the potential to step down to this and deeper persistent weakness resulting very large avalanches.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Whumpfing, shooting cracks and recent avalanches are all strong indicators of unstable snowpack.Be aware of the potential for large avalanches due to the presence of deeply buried weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 4

Wind Slabs

Touchy fresh wind slabs are likely lurking below ridgecrests and behind terrain features at higher elevations.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Use ridges or ribs to avoid pockets of wind loaded snow.Avoid freshly wind loaded features.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Loose Wet

Loose wet sluffs are expected in steep terrain features at lower elevation. Although generally slow moving, they can easily take you for a ride and run significant distances. They also have the potential to trigger slabs on the slopes below.

Avoid avalanche terrain during periods of rain.If triggered the loose wet sluffs may step down to deeper layers resulting in large avalanches.Use extra caution on slopes if the snow is moist or wet.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Feb 16th, 2017 2:00PM