Avalanche Forecast

Issued: Dec 24th, 2020 4:00PM

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

Ian Jackson,

Email
http://www.pc.gc.ca/apps/links/goto_e.asp?destination=http://avalanche.ca/spaw/2020-12-23-spaw

It's a tricky snowpack in many parts of the forecast region with a lot of variability with recent winds, snowfall and multiple weak layers.

There is a Special Avalanche Warning in effect. Click Here to access.

Merry Christmas!

Summary

Weather Forecast

Friday will be sunny with an alpine inversion and moderate to strong southwest alpine winds. Alpine temperatures will be in the -5 to -10 range whereas the valleys will stay colder. Saturday and Sunday we'll see light winds, light snow and temperatures in the -5 to -15 range.

Snowpack Summary

Winds from a variety of directions have blown the ~60cm of snow from the past week into wind slabs at higher elevations. The Dec 13 and Dec 7 sun crust/surface hoar/facet layers are down ~ 50cm and ~80 cm respectively. Height of snow at tree line is 80-150cm.

Avalanche Summary

Avalanche control this week produced mixed results from no result to size 3. Most were storm slabs, sometimes stepping down to persistent layers. No new natural avalanches reported or observed in Little Yoho on Thursday.  See the MIN for results of avalanche control with explosives on Mt Dennis on Thursday.

Confidence

Due to the number of field observations

Problems

Wind Slabs

An icon showing Wind Slabs

New wind slabs were formed from strong winds on Wednesday and Thursday. These are mainly found in the alpine but have been reported at treeline as well. The winds have been from many different directions so slabs may be found on a variety of aspects.

  • If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2.5

Persistent Slabs

An icon showing Persistent Slabs

There are a variety of weaker layers down ~50-80cm depending on the area. These are the Dec 7 and 13th layers of facets, suncrust, and isolated surface hoar. Their reactivity is a bit sporadic but treeline seems to be the biggest culprit.

  • Dig down to find and test weak layers before committing to a line.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

1.5 - 3

Valid until: Dec 25th, 2020 4:00PM