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Archived

Avalanche Forecast

Apr 12th, 2013–Apr 13th, 2013
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
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Glacier.

Variable spring conditions are present in the park.  Glide cracks and cornices continue to be a unpredictable hazard.  Avalanche hazard will increase during the overnight period with an incoming storm.

Weather Forecast

Light snow will begin mid-day today turning to moderate this evening through the overnight period. Light precipitation will continue over the weekend. During the storm winds will be moderate-strong southwesterly.  Freezing levels will continue to fall over this three day period.  Expect alpine temperature around -5 today. 

Snowpack Summary

Up to 60 cm of storm snow that fell two days ago, with moderate South winds have created a storm slab in the alpine and treeline. These slabs overly a crusts on most aspects.  Surface hoar has been observed at this interface above 2400 m on north aspects. Below treeline, the snowpack has become isothermal, frozen in the mornings, mush by afternoon.

Avalanche Summary

Yesterday we observed a small avalanche cycle in the new snow.  Moist loose avalanches were not reaching the end of their runnouts, but were observed up to size 2.5 along the highway corridor. On Grizzly shoulder, skier triggered size 1 avalanches occurred on steep, S/SW terrain on a crust. Glide cracks and cornices are still unpredictable hazards

Confidence

Timing of incoming weather systems is uncertain

Avalanche Problems

Storm Slabs

New, storm snow can be skier triggered.  Up to 70 cm of storm snow has created a slab on top of a crust.  Below treeline this snow is moist.  Treeline and above, south winds have loaded lee features.
The new snow will require several days to settle and stabilize.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 3

Persistent Slabs

Weak shallow areas are most sensitive. The character is stubborn to trigger, but seems to result in wide propagations (big avalanches), and is susceptible to remote triggering.
Avoid thin, rocky or sparsely-treed slopes.Carefully evaluate big terrain features by digging and testing on adjacent, safe slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely

Expected Size: 2 - 3