Avalanche Forecast
Issued: Jan 4th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
shorton,
Avalanche Canada
Natural and human triggered avalanches remain likely throughout this series of storms. Avoid avalanche terrain during periods of heavy snow, rain, and wind.
Summary
Confidence
Weather Forecast
Stormy weather continues until Friday.
MONDAY NIGHT: 10-25 cm of snow above 500 m, strong to extreme southwest wind, treeline temperatures around -3 C.
TUESDAY: Heavy snow continues with 15-30 cm of snow throughout the day, strong to extreme south wind, freezing level climbs to 1000 m in the afternoon with treeline temperatures nearing 0 C.
WEDNESDAY: Scattered flurries continue with another 15-30 cm of snow, strong southwest wind, treeline temperatures around -3 C.
THURSDAY: Another wave peaks in intensity midday with 20-30 cm of snow, strong to extreme south wind, treeline temperatures around -3 C.
Avalanche Summary
Avalanche activity has been reported continuously since New Year's Day, with widespread natural size 2-3 storm slab avalanches at all elevations and numerous human triggered avalanches in the Shames area (see photos in these MIN reports). The human triggered avalanches were size 1-1.5 and roughly 30-50 cm deep, and have shown signs of failing on a reactive weak layer beneath the storm snow (e.g. surface hoar and crusts). Reports suggest recent avalanches have only been storm slabs with the exception of a few explosive triggered avalanches that stepped down to deeper weak layers.
Snowpack Summary
A non-stop series of storms are building thick storm slabs. 50-100 cm of snow has fallen since New Year's Day and another 20-50 cm is expected on Tuesday. Given the intensity of the storm we expect a natural avalanche cycle in the newest snow, and are uncertain about whether the other 100 cm of recent snow has settled or is also going to produce avalanches. Reports from the Shames area suggest the storm snow has been reactive and bonding poorly to crust and surface hoar layers that are now an estimated 60-120 cm deep.
There were some deeper weak layers that were problematic around Christmas, including a surface hoar layer and a melt-freeze crust with weak facets around it. These layers were particularly problematic in the Nass Valley, Sterling, and Beaupre riding areas. These layers are now 100-200 cm deep and could be stressed by the intense load of the new snow, but will likely be inactive once the storm ends.
Terrain and Travel
- Only the most simple non-avalanche terrain free of overhead hazard is appropriate at this time.
- Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
Another intense storm pulse will cause widespread storm slab avalanche activity, especially in exposed terrain where there will be significant wind loading. At lower elevations raising freezing levels could produce wet loose avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
The heavy load of storm snow could be stressing weak layers 100-200 cm beneath the surface and produce very large avalanches that run to the ends of avalanche paths.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 5th, 2021 4:00PM
