Avalanche Forecast

Issued: Feb 26th, 2013 9:44AM

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

Avalanche Canada jfloyer, Avalanche Canada

Difficult and dangerous conditions remain in the backcountry at this time. Choose cautious and conservative routes.

Summary

Confidence

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

Weather Forecast

Synopsis: Mostly dry until Friday, when a Pineapple Express is likely to impact this region with warm temperatures and moderate (but prolonged) precipitation amounts.Wednesday and Thursday: Generally dry but flurries possible. Freezing level around 1300 m. Winds southwest, mostly light, increasing to strong on Thursday afternoon.Friday: Moderate snow/rain. Freezing level up to 2000 m. Southwesterly ridgetop winds to 60 km/h.

Avalanche Summary

A large avalanche was remotely triggered from a flat ridge on Tuesday, with a fracture depth of 130 cm. On Monday, numerous natural and human-triggered avalanches were reported up to size 2, mostly running on the February 12th surface hoar.The number, size, and destructive potential of recent avalanche events speak to the touchy nature of the persistent avalanche problem. I would expect human triggering at this persistent interface to be a very real possibility throughout the week.

Snowpack Summary

Moderate to locally heavy snowfall on Sunday adds to ongoing potent storm instabilities which seem to be most reactive as a wind slab in exposed terrain or as loose snow in more sheltered areas. A weak surface hoar layer which was buried on February 12th now exists up to a metre below the surface in many places. The highly variable and destructive nature of this persistent weakness remains a primary concern for professionals in the region. This interface has also shown reactivity on southerly aspects where a sun crust also exists. The mid to lower snowpack are generally strong and well settled. I anticipate significant cornice growth with the current weather pattern, and expect them to be weak and potentially destructive.

Problems

Persistent Slabs

An icon showing Persistent Slabs
Numerous large avalanches are failing on a weak and reactive layer of surface hoar which now lies up to 100cm below the surface. Triggering this weakness may result in surprisingly large avalanches.
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Avoid open slopes and convex rolls at all elevations where buried surface hoar may be preserved.>Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 6

Wind Slabs

An icon showing Wind Slabs
Snow and wind on Sunday night adds to an ongoing storm instability. Watch for increased slab reactivity in wind-affected terrain. In sheltered areas, the new snow may also react as a loose dry avalanche.
Avoid freshly wind loaded features.>Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 5

Valid until: Feb 27th, 2013 2:00PM

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