Avalanche Forecast

Issued: Mar 4th, 2013 9:37AM

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

triley, Avalanche Canada

Northwest Inland.

Summary

Confidence

Fair - Due to limited field observations for the entire period

Weather Forecast

Synopsis: A ridge of High pressure is expected to bring mostly clear skies and light East-Northeast winds for the next 2-3 days. Alpine temperatures should be about -9.0 and the freezing level is forecast to drop to valley bottoms overnight and only rise to about 600 metres during the day.

Avalanche Summary

A natural cycle to size 2.5 was reported from last week's storm. Small (size 1) soft slab avalanches could be triggered in response to ski-cutting at treeline on north aspect slopes through the whole week. On Thursday, a size 1.5 avalanche was human-triggered below treeline on a north aspect running on a melt-freeze crust.

Snowpack Summary

Recent storm snow amounts are 30-50 cm in the west of the region and more like 10 cm in the east. Strong southwest winds have formed touchy wind slabs in exposed terrain in the lee of ridges, gully side walls, and behind terrain features. There are a variety of old interfaces now down 60 - 100cm which include facets, crusts and isolated pockets of surface hoar. Recent observations indicate that these weaknesses have bonded fairly well now, but I still suggest digging and testing the snowpack to confirm.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 in northern and eastern parts of the region. 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

Storm Slabs

Storm slabs may remain in the west and the south of the region where there were deeper recent snow amounts. Watch for snow weakening on sun-warmed slopes.

Be cautious of sluffing in steep terrain.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

1 - 4

Wind Slabs

Wind slabs may be found behind terrain breaks. Large fragile cornices are also a concern at the moment.

Avoid travelling in areas that have been reverse loaded by winds.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Valid until: Mar 5th, 2013 2:00PM