Avalanche Forecast
Issued: Dec 12th, 2019 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
ahanna,
Avalanche Canada
New snow sitting on a layer of surface hoar may be a recipe for thin but reactive storm slabs over the next few days.
Summary
Confidence
Weather Forecast
Thursday Night: Scattered flurries accumulating up to 5 cm in some parts of the region. Alpine low -6, light northwest wind.
Friday: Cloudy with isolated flurries accumulating up to 5 cm in some parts of the region. Alpine high -4, light west wind.
Saturday: Mostly cloudy with isolated flurries accumulating 5 cm, alpine high -5, light northwest wind.
Sunday: Cloudy with sunny periods and isolated flurries, alpine high -7, northwest wind increasing to moderate.
Avalanche Summary
On Thursday, we received many reports of sloughing and small loose snow avalanches up to size 1. Reports of soft storm slabs propagating at ridgetops but breaking up quickly as they ran, were also limited to size 1.
Prior to the new snow, natural and skier triggered windslab and persistant slab avalanches averaging size 2 were widely reported in the north of the region and in neighboring Glacier National Park. Natural events have been reported on a range of aspects and are suspected to have been triggered by wind loading or solar radiation. Keep in mind that the new snow, or small storm slab avalanches could also act as triggers to these deeper avalanches.
Snowpack Summary
Thursday saw 15-20 cm of snowfall in the Monashees, with 5-10 cm elsewhere in the region. The new snow covered a widespread layer of large, feathery surface hoar crystals.
The new snow also buried soft wind slab found in the lee of features such as ridge tops, ribs and gulleys.
A weak layer formed in late November is now buried around 1 m below the surface. This is the layer of concern relating to the persistent slab avalanche problem. The weak layer may present as surface hoar, a crust, facets or a combination, depending on elevation and aspect. It can most likely be found in areas sheltered from the wind, but open to a view of the sky, such as near treeline. Below this, variety of crusts from late October are buried deeper in the snowpack.
Problems
Storm Slabs
5-20 cm of new snow fell yesterday over a layer of feathery surface hoar crystals. This can be a recipe for touchy storm slab avalanches, sometimes involving remote triggers and wide propagation. The new storm snow also hides wind slabs that have surprised a number of riders over the last few days.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
This weak layer formed in late November may present as surface hoar, a crust, facets or a combination, depending on elevation and aspect. It is buried 70-120 cm below the surface and can most likely be found in areas sheltered from the wind, but open to a view of the sky, such as near treeline.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 13th, 2019 5:00PM
