Avalanche Forecast

Issued: Feb 19th, 2013 8:42AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs, Persistent Slabs and Cornices.

Avalanche Canada ghelgeson, Avalanche Canada

Summary

Confidence

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

Weather Forecast

Wednesday: Freezing Level: 500m Wind: SW, initially moderate increasing to strong by sundown.  5 – 10 expected during the day. Thursday: Freezing Level: 500m Wind: Strong SW backing off of to moderate SW in the evening.  5 - 15 cm expected during the day. Friday: Freezing Level: 500m Wind: Strong S decreasing to light W after dark.  10 -25 cm expected during the day.

Avalanche Summary

Soft slabs up to 25 cm in depth on N aspects around 1400m were reported Monday.  Yet another size 3 avalanche that went to ground was reported Monday on a rocky convexity with a shallow snowpack.  This was in the same area where a wind loaded NE facing slope around 1400m released naturally to ground resulting in a size 3 avalanche on Sunday.

Snowpack Summary

The storm on Friday the 19th left between 20 - 60 cm in it's wake with the Northern portion of the region receiving the most snow along with a significant amount of wind that created large deep hard slabs.  Most of the precip from the last storm fell as rain below 1200m or so which resulted in a crust below treeline.  The region received another 20 cm or so Monday along with some moderate winds from both the west and possibly even east which created soft slabs that were sensitive to skier triggering on Monday.There are a variety of old interfaces now down 40 - 100cm which include facets, crusts and isolated pockets of surface hoar.  There is very limited information about the nature of this interface. I would stress the importance of digging down to find and test weak layers.A strong mid-pack currently overlies a weak base layer of facets/depth hoar. It is worth noting that the snowpack in general is quite shallow compared to averages; triggering the basal weakness may still be possible from thin spots, rocky outcrops or under the weight of larger triggers such as cornice fall.

Problems

Wind Slabs

An icon showing Wind Slabs
The region received a small shot of snow Monday along with east winds.  These reverse winds may have formed soft slabs in unusual locations.  Fresh slabs are likely hiding deep old slabs that may be rider triggerable in steep unsupported terrain.
Be cautious as you transition into wind affected terrain.>Be aware of the potential for wide propagations due to the presence of hard windslabs.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Persistent Slabs

An icon showing Persistent Slabs
Buried beneath the new snow sits a surface hoar/crust/facet weakness down 40 - 100 cm. This may be sensitive to rider triggering in steeper sheltered terrain or over convex rolls, especially at treeline elevations.
Be aware of the potential for full depth avalanches due to deeply buried weak layers.>Avoid thin spots where it may be possible to trigger large destructive avalanches.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 7

Cornices

An icon showing Cornices
The recent snow and wind have been building cornices on lee features. These cornices are likely weak and may fail at anytime. Cornice failure has the potential to trigger large avalanches.
Extra caution needed around cornices with current conditions.>Give cornices a wide berth when travelling on or below ridges.>

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 5

Valid until: Feb 20th, 2013 2:00PM

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