Avalanche Forecast

Issued: Apr 6th, 2018 4:00PM

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

tim haggarty, Parks Canada

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.

Summary

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

Dig down to test the bond to the Mar 15 crust, bearing in mind that the bond can vary significantly with subtle changes in slope aspect and steepness. Forecasters suspect this problem is developing with faceting on the crust due to recent cold temps

Be cautious with convexities and steep slopes on solar aspects.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2.5

Wind Slabs

Expect to encounter smaller windslabs in the alpine. They range from 20-40cm thick and have been decreasing in sensitivity over the last couple of days. Watch for the incoming storm to establish new slabs Saturday and Sunday.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Apr 7th, 2018 4:00PM