Avalanche Forecast
Issued: Dec 13th, 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
20-30 cm of new snow rests on a layer of surface hoar. Expect it to become touchy as it settles into a storm slab in the mild temperatures. Watch for shooting cracks and electric propagation, especially near openings in the trees.
Summary
Confidence
Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.
Weather Forecast
Friday Night: Cloudy with clear periods and isolated flurries. Alpine low -8, light northwest wind.
Saturday: Cloudy with sunny periods and isolated flurries, alpine high -6, light northwest wind.
Sunday: Cloudy with sunny periods and isolated flurries, alpine high -7, moderate northwest wind.
Monday: A mix of sun and cloud, alpine high -9, moderate northwest wind.
Avalanche Summary
Reports from Thursday and Friday mostly describe sloughing and small loose dry avalanches up to size 1. 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
20-30 cm of new snow has covered a widespread layer of large, feathery surface hoar crystals. The new snow can be expected to gain cohesion and settle into a slab in the mild temperatures, especially at treeline and below.
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
20-30 cm of new snow is expected to gain cohesion and settle into a slab in the mild temperatures, especially at treeline and below. It sits over a widespread weak layer of large, feathery surface hoar crystals. This can be a recipe for touchy storm slab avalanches, sometimes involving remote triggers and wide propagation.
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 around 1 m below the surface and can most likely be found on steep south-facing slopes or in areas sheltered from the wind, but open to a view of the sky.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 14th, 2019 5:00PM
