Avalanche Forecast
Issued: Feb 21st, 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
Avoid wind loaded slopes and pay close attention to changing conditions throughout the day as avalanche danger will increase throughout the storm.
Summary
Confidence
Weather Forecast
A warm front crossing the region Monday will bring 15-25 cm of snow with mild temperatures and strong wind.
SUNDAY NIGHT: Cloudy with scattered flurries bringing 5-10 cm of snow, strong southwest wind, freezing level climbing to 1200 m with treeline temperatures around -4 C.
MONDAY: Cloudy with scattered flurries and another 5-15 cm of snow, strong west wind, freezing level around 1300 m with treeline temperatures around -2 C.
TUESDAY: Mix of sun and cloud, light wind, treeline temperatures drop to -8 C.
WEDNESDAY: Sunny, light wind, treeline temperatures around -8 C.
Avalanche Summary
Steady pulses of snow since Wednesday have resulted in surprisingly little avalanche activity. On Friday and Saturday there were some small dry loose avalanches and some small (size 1) skier triggered snow slab avalanches. Explosive control on Friday produced a few larger (size 2) slabs on bigger terrain features that were up to 50 cm thick.
There were many reports of human triggered persistent slab avalanches during the first two weeks of February. These avalanches failed on a surface hoar layer that is now 50-100 cm deep and is most prevalent at treeline elevations. There have also been 2 very large explosive triggered avalanches in the Bonningtons in the past month (most recently on Feb 9) that stepped down to the early December crust to produce a 200 cm deep, size 3.5 avalanche.
Snowpack Summary
It has been snowing steadily for several days, but no single pulse big enough to form reactive storm slabs. The final pulse on Monday could bring recent storm totals to 30-50 cm, which may be enough for storm slab formation to be a serious concern. The main persistent layer of concern is a combination of surface hoar, facets, and crust layers that formed in January that are now buried 50-100 cm deep. An early season crust near the bottom of the snowpack has periodically produced avalanches in thinner snowpack areas. These persistent layers have appeared to gone dormant in the past week, but could re-emerge as a problem with the incoming weather.
Terrain and Travel
- Travel in alpine terrain is not recommended.
- Avoid freshly wind loaded terrain features.
- Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
- Watch for fresh storm slabs building throughout the day.
- Choose slopes that are well supported and have limited consequence.
Problems
Storm Slabs
Fresh snow continues to gradually accumulate and could be forming reactive slabs, especially on steep and wind loaded slopes.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A buried persistent weak layer still lingers 50-100 cm deep. Despite limited recent avalanche activity, the gradual load of new snow and mild temperatures could be adding stress to this layer. This surface hoar/crust interface may remain human triggerable in steep convex features at treeline and potentially steep alpine features where it presents as a crust.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 22nd, 2021 4:00PM
