Avalanche Forecast
Issued: Jan 5th, 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
Avalanche danger remains HIGH as the storm rages on. Avoid all avalanche terrain during periods of heavy snowfall and wind.
Summary
Confidence
Weather Forecast
The storm rages on until Wednesday morning then light flurries continue.
TUESDAY NIGHT: 15-25 cm of snow, strong southwest wind, treeline temperatures around -4 C.
WEDNESDAY: Scattered flurries continue with 10-20 cm of snow throughout the day, strong southwest wind, treeline temperatures around -2 C.
THURSDAY: 5-10 cm of snow by the morning then clearing skies in the afternoon, strong south wind, treeline temperatures around -5 C.
FRIDAY: Cloudy skies and isolated flurries with up to 5 cm of snow, moderate south wind, treeline temperatures around -5 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 and Terrace area (see photos in these MIN reports). The human triggered avalanches have been size 1-2 and roughly 30-70 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 involved snow that has fallen since New Year's, 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. 75-125 cm of snow has fallen since New Year's Day and another 20-40 cm is expected on Wednesday. Given the intensity of the storm we expect a natural avalanche cycle in the newest snow, and are uncertain about whether the other metre of recent snow has settled or is still 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
The final storm pulse on Wednesday will bring 20-40 cm of snow, resulting in another round of storm slab avalanche activity. Natural activity will be especially likely in higher open terrain where there will be significant drifting, while human triggering remains likely on all steep slopes. Storm slabs have been very reactive in the Shames area, as they seem to be sitting above touchy surface hoar and crust layers.
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 6th, 2021 4:00PM
