Avalanche Forecast

Issued: Feb 5th, 2013 9:41AM

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

Avalanche Canada mpeter, Avalanche Canada

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Wednesday: Expect mostly cloudy skies with a chance of flurries. Winds should be light southerly and alpine temperatures should reach -6.Thursday: We should see a mix of sun and cloud with winds turning westerly then northwesterly and strengthening. Alpine temperatures should again reach around -6.Friday: Clouds return with a slight chance of flurries. Winds settle back to westerly and increase to moderate/strong values. Expect temperatures around -6.

Avalanche Summary

The region has seen a natural avalanche cycle. Natural slabs and cornice falls up to size 3.0 have been reported, predominantly on north-northeasterly terrain. Many loose wet avalanches up to size 2.0 have occurred below treeline, where the recent precipitation fell as rain. Both explosive and rider controlled avalanches have also been observed up to size 2.5, predominantly in wind loaded areas. Some areas are reporting reverse loading from changing wind directions and have seen windslab failures in southeast facing terrain features.

Snowpack Summary

The recent storm has past, bringing cooler temperatures and a lull in precipitation. The storm snow is settling very quickly. Below 1000m, much of the precipitation fell as rain and the low elevation snowpack remains moist below the recently formed crust.The tail of the storm brought strong southwest winds, giving intense snow transport and cornice growth. Extensive windslabbing in lee zones and behind ridges in the alpine and treeline was the result. Large cornice failures are possible. Some areas saw swirling winds resulting in some cross and reverse loading on southeasterly features.In the upper snowpack, a thin melt-freeze crust buried on Jan. 17 and a persistent weakness of surface hoar and/or facets remain a concern. I'm thinking the new storm load will accelerate the bonding process and put these layers to bed, but its worth keeping them on your radar in regards to distribution and reactivity for the short term. The mid and lower snowpack is generally well settled and strong, but basal facets remain a concern in the northern part of the region.

Problems

Storm Slabs

An icon showing Storm Slabs
Some areas may have up to 75-100 cm of recent storm snow at upper elevations. SW winds have built fresh windslabs in lee features and behind ridgecrests. Warm temperatures have promoted rapid settlement and slabbing in open areas.
The new snow will require several days to settle and stabilize.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 5

Cornices

An icon showing Cornices
The recent weather was prime for cornice growth.
Extra caution needed around cornices with current conditions.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 6

Persistent Slabs

An icon showing Persistent Slabs
Persistent weaknesses in the upper snowpack (Jan. 17 crust & a deeper facet/surface hoar interface) may linger. Local investigation to test the distribution and reactivity of these layers is a good idea before committing to steep slopes.
Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 7

Valid until: Feb 6th, 2013 2:00PM