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Archived

Avalanche Forecast

Feb 22nd, 2013–Feb 23rd, 2013
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Glacier.

A strong storm today and tonight will rapidly increase avalanche hazard in the park.  We are expecting widespread natural activity and touchy conditions for riders. Keep your plans flexible and adjust them accordingly.

Weather Forecast

A strong fast moving storm will move across the park today and tonight.  The most intense period of the storm will be this afternoon with strong westerly winds, possibly gusting to extreme.  Up to 30 cm of snow are forecast for today and another 10 cm tonight.  Light snow will continue Saturday with moderate snow for Sunday in the forecast.

Snowpack Summary

10cm of low density snow overnight overlies hard and soft slabs.  Hard slabs can be found in isolated lee features in the alpine deposited from southerly winds. Soft slab overlies a surface hoar layer down 30-50cm. This layer has been gaining strength but could still be reactive, especially between 17-1900m and where it sits on a sun crust.

Avalanche Summary

We have not observed any new natural activity in the past few days.  There has also been a lack of observation or reports of skier-triggered avalanches on the Feb 12 surface hoar.  Both natural and rider-triggered avalanche activity will increase with the incoming storm today.  Avalanche control Wednesday produced a several avalanches to size 2.5. 

Confidence

Forecast snowfall amounts are uncertain

Avalanche Problems

Persistent Slabs

A weak layer is down 40-50cm. It is most likely to be skier-triggered around 17-1900m, avoid open slopes and convex rolls. On sunny aspects the weak layer can be touchy.  Natural avalanche activity will increase on this layer today with the new snow.   
Choose conservative lines and watch for clues of instability.Avoid avalanche terrain during periods of heavy loading from new snow and wind.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Wind Slabs

Wind slabs persist in lee loaded features near ridge crests and roll-overs. Strong winds today will rapidly change conditions in the alpine and open areas at treeline today.
Assess start zones carefully and use safe travel techniques.Avoid freshly wind loaded features.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2