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Archived

Avalanche Forecast

Nov 28th, 2018–Nov 29th, 2018
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
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
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Sea To Sky.

We're working from very few observations right now, but it looks wet and soggy at lower elevations. The exception is in the alpine where storm slabs and cornices pose a serious threat. Please let us know what you're seeing on the MIN!

Confidence

Low - Due to the number of field observations

Weather Forecast

The storm has passed, and we are slowly transitioning towards a period of pronounced high pressure. The forecast period is marked by cooler temps, very little precipitation and the potential for clear skies by the weekend.WEDNESDAY NIGHT: Freezing level holding around 1000 m, light variable wind, trace of precipitation possible. THURSDAY: Scattered cloud cover, freezing level around 1000 m, light variable wind, no significant precipitation expected.FRIDAY: Broken cloud cover, freezing level around 1000 m, light southwest wind, no significant precipitation expected.SATURDAY: A few clouds, freezing level around 700 m, light east/northeast wind, no significant precipitation expected.

Avalanche Summary

Skies cleared Tuesday allowing some observation of avalanches that likely released at the height of the storm. A large (size 2.5) avalanche was reported on a northeast facing glacial feature between 2100 and 2200 m. The avalanche failed naturally with a crown up to 1 meter in depth. Another large natural avalanche (size 2) was reported from a north facing feature near 2000 m. Several natural loose wet avalanches to size 1.5 were also reported from treeline.Please submit any observations you have to the Mountain Information Network here,

Snowpack Summary

Monday and Tuesday's intense precipitation event rain-soaked the existing snowpack up to about 1800 m and left 20 to 30 cm of wet snow in place up to 2000 m. Above 2000 m the storm produced around 60 cm of new snow. The upper 20 cm of snow is reportedly dry in the alpine. Strong to extreme wind on Monday and Tuesday formed storm slabs, cornices, and wind damaged snow in high elevation alpine terrain. Above 2000 m, 50 to 150 cm of snow now sits on the early November crust/facet interface. Little is known about the reactivity of this interface in the alpine. This crust may be associated with weak faceted crystals in some places where it lies close to the ground. This is most likely to cause problems in glaciated terrain or on smoother, high elevation slopes where the summer snow did not melt out.

Avalanche Problems

Storm Slabs

Soft slabs up to 20 cm in depth exist in the alpine. Cooling temperatures will likely reduce the slabs sensitivity to human triggering, but you need to be mindful of this problem, especially in extreme terrain and immediately lee of ridgecrest.
Be cautious around mid-slope terrain features like ridges and ribs where slabs may be deeper.Use caution in alpine lees. Recent snowfall mixed with wind loading has created storm slabs.If triggered, storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1 - 2

Cornices

Cornices have formed on many alpine ridgelines.  These cornices may be large and weak.  Do not trust them and avoid travel on or underneath them. 
Extra caution needed around cornices with current conditions.Do not travel on slopes that are exposed to cornices overhead.Stay well back from cornices when traveling on ridgelines.

Aspects: North, North East, East, North West.

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1 - 2