Avalanche Forecast

Issued: Mar 18th, 2016 8:22AM

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

pmarshall, Avalanche Canada

Northwest Coastal.

Extra caution is needed in areas in the northern part of the region where buried persistent weaknesses remain active.

Summary

Confidence

Moderate

Weather Forecast

SATURDAY: Mainly cloudy. The freezing level dips to 1300 m. Winds should be moderate from the S-SE. SUNDAY: Cloudy with a chance of flurries. The freezing level spikes back to 1600-1800 m and winds are light to moderate from the east. MONDAY: Cloudy with light snow. The freezing level is around 1200-1400 m and winds are light.

Avalanche Summary

On Thursday, there were reports of natural and explosive-triggered cornice falls, primarily from areas north of Stewart and near Ningunsaw Pass. Many of these triggered persistent slabs with the largest results (size 3-3.5) occurring on NE-NW aspects. Observations from the southern part of the region were limited, but one observer reported triggering storm slabs up to 20 cm deep (size 1-1.5) on north-facing slopes.

Snowpack Summary

Easterly winds have redistributed the surface snow forming fresh wind slabs in exposed terrain. On sheltered and shady slopes there is 20-40 cm of settled dry (and faceting) powder, possibly capped by surface hoar. On south aspects, the recent storm snow may be sitting on a sun crust. Lower elevations and south aspects are going through daily melt-freeze cycles. A layer of surface hoar or melt-freeze crust buried on March 3 is down 70-100cm and has been recently reactive in the areas north of Stewart. An older crust/facet layer buried in early February can now be found down over a meter but this layer has been dormant for several weeks.

Problems

Cornices

Natural cornice releases are possible with sun exposure and warming. A falling cornice chunk could trigger a large slab on the slope below.

Cornices become weak with daytime heating. >Extra caution needed around cornices with current conditions.>

Aspects: North, North East, East, South East.

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 5

Wind Slabs

Recently easterly outflow winds may have created fresh wind slabs in exposed terrain.

Be cautious as you transition into wind affected terrain. >Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

Persistent weaknesses have recently been reacting to cornice triggers in the northern part of the region. Keep these in mind if you're riding near Bear Pass or Ningunsaw Pass.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar. >Dig down to find and test weak layers before committing to a big slope. >

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Mar 19th, 2016 2:00PM