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Archived

Avalanche Forecast

Apr 11th, 2013–Apr 12th, 2013
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
3: Considerable
The avalanche danger rating below treeline will be considerable
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
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.

We are in a heavy storm cycle.  Expect permit area closures until things settle out.

Weather Forecast

An unstable airmass will linger over the area today, bringing clouds and flurries.  Things will dry out overnight, but another front is due to arrive on Friday, bringing another 13+mm of precipitation to the area tomorrow.  The weekend promises to be unsettled as well, with improving weather for Monday.

Snowpack Summary

35 cm of storm snow overnight with moderate to strong South winds have created a storm slab in the alpine and treeline.  These slabs overly crusts on solar aspects and facets or surface hoar on north aspects.  The SH is best preserved above 2400m.  Below treeline, the snowpack has become isothermal, frozen in the mornings, mush by afternoon.

Avalanche Summary

A widespread natural avalanche cycle occurred late yesterday and over night with the addition of heavy wet storm snow, up to size 3, running to valley bottom. Glide cracks and cornices are growing larger, and are failing unpredictably.  Heavy loading overnight will make things touchy today.

Confidence

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

Avalanche Problems

Storm Slabs

40 cm of heavy moist storm snow overnight with steady south winds has created slabs at and above treeline.  This layer will be touchy today, especially as temperatures warm up.
Watch for terrain traps where small amounts of snow will acumulate into deep deposits.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 3

Deep Persistent Slabs

Glide cracks, gaping cracks in the snowpack, exist on many slopes and have been failing with warm temps. They can fail unpredictably and release the entire snowpack to the ground.  The  overnight storm snow may provide a trigger for deep releases
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.Avoid areas with overhead hazard.

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.
Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Avoid shallow snowpack areas where triggering is more likely.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely

Expected Size: 2 - 3