Avalanche Forecast

Issued: Mar 14th, 2015 9:43AM

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

triley, Avalanche Canada

South Rockies.

Forecast snow and wind are expected to increase the avalanche danger. Be prepared for winter conditions at higher elevations.

Summary

Confidence

Poor - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The first wave of precipitation and strong southwest winds is expected to end Saturday evening, and there should be a short break before the next wave starts on Sunday. The freezing level should gradually drop on Sunday, with most of the forecast 10-15 mm of precipitation coming as snow above 1000 metres combined with moderate easterly winds. Snow/rain should end late Monday morning or early afternoon, but remain cloudy. Mostly cloudy with a chance of sunny periods on Tuesday as the freezing level rises to about 2200 metres.

Avalanche Summary

No new avalanches reported. On Tuesday, our field team members in the north Elk Valley experienced several whumpfs on south facing treed terrain at 2200 m. They also experienced a whumpf of a hard slab near ridge top at 2450 m and saw a deep slab release on a sunny aspect that probably occurred some time in the last week. Recent loose wet avalanches up to size 1.5 appeared to have been triggered by solar warming. On Sunday, a skier-triggered slab released on a weak layer near the ground in Kananaskis Country. Rain, snow and wind forecast for the weekend are likely to drive natural avalanche activity.

Snowpack Summary

Rain is likely to weaken the snowpack below about 2000 m on Saturday, and may cause a natural cycle of loose wet or wet slab avalanches. At low elevations, thin snowpack areas may simply melt. On the highest peaks, new snow will probably be shifted by strong winds into slabs lee to the SW. Cornices may develop. The most prominent snowpack feature is a thick crust 10-30cm below the surface, extending up to around 2200m elevation. The support of this crust is breaking down in response to warm temperatures. Persistent weak layers below this crust still react in snowpack tests and could wake up with continued warming or loading.

Problems

Loose Wet

Rain combined with no re-freeze has increased the likelihood of loose wet and possibly wet slab avalanches.

Avoid steep or committing slopes if the snow is moist or wet.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Deep Persistent Slabs

Several days of warming followed by rain up to alpine elevations may result in avalanches releasing down to persistent weak layers. Avalanches releasing or stepping down to deeply buried weak layers may result in large destructive avalanches.

Avoid large slopes during times of warm temperatures.>Be aware of thin areas and rock outcroppings where you are more likely to trigger a deep slab.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Wind Slabs

New snow and strong winds at high alpine elevations may have developed new windslabs that may be easy to trigger. Expect windslab development to continue with forecast precipitation and dropping freezing levels.

Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Mar 15th, 2015 2:00PM