Avalanche Forecast
Issued: Dec 21st, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs, Storm Slabs and Loose Dry.
Ian Jackson,
Avalanche Control is planned for Mt. Stephen, Mt Field and Mt. Dennis on Tuesday December 22. No access to these areas!
Summary
Weather Forecast
An early christmas present of 15-20 cm has started to fall as I write this bulletin. This is forecast to fall with mostly light southerly winds which will switch to north and become strong at the tail end of the storm. Tuesday looks cool with clearing skies. Wednesday and Thursday look sunny and cold with lows near -20 and increasing alpine winds
Snowpack Summary
30-60cm over the last week have been redistributed by strong west winds forming windslabs in exposed alpine and treeline areas. The Dec 13 and Dec 7 sun crust/surface hoar/facet layers are down ~ 35cm and ~65cm respectively. The Nov crust/facets sit at the bottom of the snowpack and are generally well bonded. Height of snow at tree line is 80-150cm
Avalanche Summary
A field trip to treeline on Mt Field today revealed a less touchy snowpack than expected. No new avalanches seen and surprisingly no whumphing or reactivity on steep rolls TL and BTL. However, the Dec. 13th surface hoar layer was found in a test pit at 1950 m and produced an ECTP 26 result down 65 cm on well preserved 3-5 mm surface hoar.
Confidence
Problems
Persistent Slabs
The new load will likely awaken the Dec. 7th surface hoar/facet/sun crust layer which is down 30 -70 cm in this area and is fairly widespread. Reign in your terrain choices!
- Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
- Avoid avalanche terrain.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Storm Slabs
15-20 cm is expected overnight Monday. We expect this to slide easily until it has had time to settle. These storm slabs could potentially trigger the persistent slab problem.
- If triggered the storm slabs may step down to deeper layers resulting in large avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Loose Dry
With the incoming snow, loose dry avalanches will run in gully features and steep terrain.
- Minimize overhead exposure during periods of heavy loading from new snow, wind.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 22nd, 2020 4:00PM
