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Avalanche Forecast

Archived

Apr 6th, 2018–Apr 7th, 2018

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Little Yoho.

A skier triggered avalanche yesterday afternoon highlights the serious nature of the March 15 persistent slab problem. Watch for increasing avalanche hazard through the weekend with incoming new snow.

Weather Forecast

Continued flurries overnight Friday with more significant snowfall expected on to start mid afternoon Saturday with and increase in temperatures. Expect both the new snow and the increasing temperatures to lead to an increase in the avalanche hazard. Further increases in temperature can be seen in long term forecasts, a significant change to watch.

Snowpack Summary

Trace amounts of new snow in the past 18 hours. Last week's storm brought 15-40cm with moderate S and W winds creating wind slabs in the alpine. The March 15 suncrust is down 25-50cm on south-east through west aspects and has been sensitive to skier triggering over the last few days.

Avalanche Summary

Visitor Safety responded to Sentinel Pass for a skier accidental avalanche reported by the involved party via In-reach at approx 1700hrs April 5. Avalanche failed on March 15 crust persistent layer that has been sensitive to skier triggering for a couple of weeks ... 20-50cm deep at 2575m ,SE aspect, 200mx200m. Impressive save by party members.

Confidence

Intensity of incoming weather systems is uncertain on Saturday

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.