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Archived

Avalanche Forecast

Apr 10th, 2013–Apr 11th, 2013
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
4: High
The avalanche danger rating in the alpine will be high
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

Regions: Glacier.

A substantial storm is expected today, with high SW-NW winds and up to 25mm of precipitation.  This will bump hazard up to HIGH tomorrow in the alpine, but be aware that it could get there later today.

Weather Forecast

A Pacific frontal system will bring moderate precipitation and strong winds to the area today.  Winds will shift from SW to NW throughout the day, potentially resulting in reverse loading of snow onto south aspects.  Expect thick cloud and mild temperatures.  Tomorrow should be a nicer day, drier, maybe even some sun.

Snowpack Summary

Variable Conditions.  In the alpine, SSL and HSL from last weeks storm and wind event overly crusts on solar aspects and facets or surface hoar on north aspects.  The SH (from April 4)  is best preserved above 2400m, and is reactive to skier triggering.  Below treeline, the snowpack has become isothermal, frozen in the mornings, mush by afternoon.

Avalanche Summary

A few isolated avalanches were noted yesterday, and reports of "whumping" by skiers, mostly in the alpine.  Glide cracks and cornices are growing larger, and are failing unpredictably.  Three days ago, a size 3.0 natural slab avalanche in Youngs Peak Basin and a skier remotely triggered size 2.5 - 3 off of Youngs Peak Headwall. 

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Wednesday

Avalanche Problems

Wind Slabs

Hard and Soft Slabs were observed in the alpine, near ridge crests and on convexities, all aspects.  Additional snow and wind today will add to this problem
Avoid travelling in areas that have been reverse loaded by winds.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Deep Persistent Slabs

Glide cracks, gaping cracks in the snowpack, exist on many slopes and have been failing with the warm temps. They can fail unpredictably and release the entire snowpack to the ground.
Be aware of thin areas that may propogate to deeper instabilites.Give cornices a wide berth when travelling on or below ridges.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 4

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. 
Travel early before the heat of the day, and avoid big slopes in the afternoon.Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely

Expected Size: 2 - 3