Avalanche Forecast

Issued: Apr 16th, 2016 9:27AM

The alpine rating is below threshold, the treeline rating is below threshold, and the below treeline rating is below threshold. Known problems include Wet Slabs, Cornices and Loose Wet.

jsmith, Avalanche Canada

Purcells.

Spring Conditions. Ongoing sunny weather and rapidly rising freezing levels will increase the likelihood of large destructive wet slab avalanches, especially if there is little or no overnight refreeze of the snow surface.

Summary

Weather Forecast

SUNDAY: Freezing Level: 3000m, sunny, light southerly winds. MONDAY:Â Freezing Level: 3600m, sunny, light southerly winds. TUESDAY:Â Freezing Level: 3600m, sunny, light southerly winds.

Avalanche Summary

No new avalanches reported in this region. Most commercial operations have closed for the season, and data is becoming sparse. However, with the forecasted warm up Sunday and especially Monday, I would expect sporadic large and destructive wet slab avalanches.

Snowpack Summary

Monitoring the overnight freeze of the snow surface is very important during the spring. If the snow surface does not freeze overnight or if the crust is only a few cm thick, the effect of daytime heating and solar radiation will weaken the snowpack much more quickly than it would if there is a well frozen thick crust. This is because the crust must first melt before the sun can weaken the snowpack. Deeply buried weak layers in the mid snowpack and near the ground still have the potential to wake up and become active with a rapid warm up. While unlikely, releases on these deeply buried weak layers would result in very large avalanches. Glide cracks are widespread, active, and best avoided. Cornices are large, fragile, and could trigger deep slab avalanches that run to valley bottoms. Low elevation and thin snowpack areas have become isothermal, meaning the snowpack is 0 degrees Celsius throughout. An isothermal snowpack is more prone to full depth wet slab avalanches during the heat of the day.

Problems

Wet Slabs

Rapidly warming temperatures and little to no overnight surface freeze will increase the potential for deep wet slab release.

Travel early before the heat of the day, and avoid big slopes in the afternoon.>Be aware of the potential for large, deep avalanches.>Avoid slopes with glide cracks.>

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

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Cornices

If the sun is shining, cornices present a significant hazard. Even if they don't trigger a slab avalanche when they fall onto a slope, they have a nasty habit of running surprisingly long distances.

Cornices become weak with daytime heating, so travel early on exposed slopes.>Cornice releases have the potential to trigger deeply buried weak layers.>Pay attention to overhead hazards like cornices.>

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Loose Wet

Solar radiation in the spring can rapidly change the hazard from low to high. Plan ahead and monitor the effect of solar radiation carefully.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Watch for surface clues such as sluffing off of cliffs and pinwheeling. These are red flags that should prompt you to reevaluate the conditions.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Apr 17th, 2016 2:00PM