Avalanche Forecast
Issued: Mar 17th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
shorton,
Avalanche Canada
Cautious route-finding is recommended right now due to uncertainty about buried weak layers, especially in the western parts of the region where there is potential for large avalanches.
Summary
Confidence
Moderate - Uncertainty is due to the complexity of the snowpack’s structure.
Weather Forecast
THURSDAY NIGHT: Cloudy with scattered flurries bringing up to 5 cm of new snow, light to moderate wind from the southwest, treeline temperatures drop to -8 with freezing level around 1200 m.
FRIDAY: Mostly cloudy with some light flurries bringing trace amounts of snow, light wind from the southwest, treeline temperatures around -4 C with freezing level around 1500 m.
SATURDAY: Mostly cloudy with flurries starting midday brining trace amounts of snow, moderate wind from the southwest, treeline temperatures around -4 C with freezing level around 1500 m.
SUNDAY: Flurries continue overnight with 5 to 10 cm of new snow by the morning then sunny breaks in the afternoon, light wind from the west, treeline temperatures around -6 C with freezing level around 1200 m.
Avalanche Summary
There were several notable human-triggered slab avalanches on Wednesday that suggested recent snow is bonding poorly to the underlying layers. These occurred on a range of aspects above 2000 m. Most slabs were small in the top 20 to 30 cm of snow (size 1), but one larger 70 cm thick slab was remotely triggered from below by a group of skiers (size 2). This avalanche occurred on a south aspect at 2250 m.
Over the past few days there have also been reports of cornice failures, small loose avalanches, and several large (size 2) wind slab avalanches in alpine terrain following Tuesday's storm.
While we are becoming less concerned about wind slabs, we have heightened concern about a developing persistent slab problem in some parts of the Purcells (read more in this blog).
Snowpack Summary
The upper snowpack is highly variable as snowfall totals over the past week have ranged from 20 cm in the eastern Purcells to 60 cm in the western Purcells. Snow depths also taper significantly with elevation, with moist and crusty surfaces below 1800 m and on south aspects into the alpine.
In some areas this snow is well bonded to old crust layers, while in other areas the snow has settled into a reactive slab above weak layers around the crusts. At this point, it appears persistent slab problems could be developing in the deeper snowpack areas along the western side of the range, while the eastern side more likely has thinner wind slabs. The lower snowpack is generally well bonded.
Terrain and Travel
- Uncertainty is best managed through conservative terrain choices at this time.
- Choose slopes that are well supported and have limited consequence.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
- Be carefull around freshly wind loaded features.
Problems
Persistent Slabs
30 to 60 cm of recent snow has potential to form a persistent slab above weak layers. There have been reports of a poor bond to underlying sun crust layers on south slopes and surface hoar crystals on north slopes.
At this point we are uncertain about how long this problem will take to heal and suggest a more conservative approach to terrain to handle this uncertainty.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Recent wind has left unstable wind slabs at upper elevations, especially along ridgetops.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 18th, 2022 4:00PM
