Avalanche Forecast

Issued: Apr 3rd, 2017 4:40PM

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

Avalanche Canada triley, Avalanche Canada

Wind slabs may continue to be reactive to human triggers. Cornices may fall off naturally, and act as a trigger for deeply buried weak layers on slopes below.

Summary

Confidence

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

Weather Forecast

Overnight: Clear with light winds and freezing down to valley bottoms. Tuesday: Mix of sun and cloud with light winds and daytime freezing up to 1500 metres. Wednesday: Overcast with increasing southwest winds and daytime freezing around 1900 metres. Thursday: A couple of cm of new snow in the morning, followed by light winds and a chance of sunny breaks. Daytime freezing may reach 2200 metres.

Avalanche Summary

On Monday there were several natural cornice falls up to size 2.5 that released storm or persistent slabs from the northerly aspect slopes below. On Sunday there was a natural cornice fall size 2.5 from extreme terrain.

Snowpack Summary

10-15 cm of recent snow now overlies temperature crusts below about 1900 metres and sun crust all the way into the alpine on solar aspects. This precipitation fell as rain below about 1600 metres. Below the new snow interface, storms over the past week brought 40-60 cm of snow to the region. Several other crusts as well as moist snow are likely to exist within this storm snow, mainly at lower elevations and on solar aspects. Moderate to strong southwest winds during and since the storm formed wind slabs on leeward slopes as well as fragile cornices along ridgelines. At higher elevations, the February crust/facet layer is now down around 130-150 cm and the deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack. These layers were active during a storm in mid-March and produced some very large avalanches. Occasional deep releases were also reported in late March and these deeply buried weaknesses remain a serious concern as solar radiation and warming temperatures begin to penetrate the snowpack at increasingly higher elevations.

Problems

Wind Slabs

An icon showing Wind Slabs
Recent southwest winds have redistributed storm snow into wind slabs at higher elevations that may remain reactive to human triggering. These slabs weaken and become increasingly reactive with daytime warming.
Use ridges or ribs to avoid pockets of wind loaded snow.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
A cornice fall or smaller slab avalanche could trigger large, destructive avalanches on deeply buried weak layers. The likelihood of this happening will increase as solar warming weakens unstable cornices and wind slabs over the course of the day.
Recognize and avoid runout zones.If triggered, wind slabs or cornices may step down to deeper layers and result in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Loose Wet

An icon showing Loose Wet
Solar warming will progressively deteriorate the surface of the snowpack at lower elevations and on solar aspects. Snow that becomes moist will have the tendency to sluff from steep terrain, either naturally or with a human trigger.
Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Apr 4th, 2017 2:00PM