Register
Get forecast notifications
Create an account to receive email notifications when forecasts are published.
Login
Archived

Avalanche Forecast

Jan 20th, 2017–Jan 21st, 2017
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Kootenay Boundary.

In the southwest corner of the region there's an unusually weak snowpack: Conditions are primed for people triggering avalanches. Don't let the lure of deep powder draw you into terrain that's inappropriate for the conditions.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Nothing too crazy for the weekend: slightly warmer than seasonal temperatures and only a few flurries are expected. Clear fine weather for early next week. SATURDAY: Mainly cloudy with the possibility of isolated flurries (local accumulations 5-10cm), light south wind. Freezing level dropping to 1000m and alpine high temperatures to -4 Celsius.SUNDAY: Flurries with another 5-10 cm possible, moderate southerly winds. Freezing levels remaining around 1000m and alpine high temps to -4 Celsius.MONDAY: Cloudy with sunny breaks. Light northerly wind and freezing level around 700m, alpine high temperatures to -3 Celsius.

Avalanche Summary

Conditions are touchy in some sections of the Rossland range: On Thursday there was a skier triggered size 2 with a full burial, running on the mid November crust, west aspect near 2000m. On Thursday several natural, explosive and human triggered storm slabs were reported primarily on northerly aspects at treeline and alpine elevations. Expect lingering human-triggered avalanche potential for the forecast period. Also, expect deeper persistent weaknesses (basal facets, mid-November rain crust, mid December surface hoar / facets) to become more reactive with the new snow, wind-loading and warm temperatures. Time to dial back the terrain use!

Snowpack Summary

By Friday morning another 2-10 cm added to the previous 25-45 cm of fresh snow this week, accompanied by moderate to strong southerly winds. This has resulted in touchy storm and wind slabs bonding poorly to the previous snow surface that includes facets and large surface hoar on sheltered slopes and/or a sun crust on steep sun-exposed aspects, as well as wind-affected surfaces (e.g. hard wind slab, sastrugi, scoured crust, etc.) in exposed areas. In some areas of the Rossland range, the mid-November rain crust / facet layer is now likely down 50-90 cm and has become reactive with continued loading and warming. In thin rocky areas, particularly in the Rossland range, recent reports include easy sudden collapse snowpack test results on facets down 120-150 cm near the ground. This deep persistent weakness may also become reactive with continued loading and warming.

Avalanche Problems

Storm Slabs

New snow is bonding poorly to the previous snow surface. Expect the avalanche likelihood and size to increase with increased snow and wind-loading. Slabs will be particulary deep and touchy on wind-loaded northerly aspects near ridge crests.
If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.The new snow will require several days to settle and stabilize.Watch for signs of instability such as whumpfing, or cracking.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 3

Persistent Slabs

Several different persistent weak layers are buried 60-150cm deep and have started to become reactive to human triggering. Conservative terrain use is essential, especially in the southwest portion of the region.
If triggered the storm slabs may step down to deeper layers resulting in large avalanches.Carefully evaluate terrain features by digging and testing on adjacent, safe slopes. Be aware of the potential for full depth avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 3