Avalanche Forecast

Issued: Feb 6th, 2013 9:26AM

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

mpeter, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Good

Weather Forecast

Thursday: Expect a mix of sun and cloud. There is a chance of low level stratus cloud close to the coast. Temperatures will be cool in the morning, but warm to around -3 with the sun’s influence. Expect light northwest winds and no precipitation.Friday: Clouds should build overnight and linger through the day. Expect flurries, focussed primarily on west facing terrain. 5-10cm are possible. Winds should turn westerly and pick up to moderate/strong values with alpine temperatures reaching -5.Saturday: Clouds linger but precipitation dissipates. Winds turn southwesterly and ease with alpine temperatures reaching around -1.

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

Recent weather has been relatively benign, with precipitation pulses giving incremental loading (5-10cm at a time). Relatively light winds have accompanied these snowfall pulses with some stronger outflow winds closer to the coast.Previous strong southwest winds gave intense snow transport and cornice growth. Extensive windslabbing in lee zones and behind ridges in the alpine and treeline was the result. Some areas saw swirling winds resulting in some cross and reverse loading on southeasterly features. These significant windslabs are now lightly buried.In the upper snowpack, a melt-freeze crust buried on Jan. 17 remains a concern. Recent compression tests show both resistent and sudden planar results and an extended column test shows a continued propensity for propagation if the layer was triggered. The Jan. 17th crust is down 60-100cm. It is certainly worth keeping this layers on your radar in regards to distribution and reactivity for the short term. The mid and lower snowpack is generally well settled and strong.

Problems

Wind Slabs

SW winds have built fresh windslabs in lee features and behind ridgecrests. Classic outflow winds have also contributed to the slabbing issue.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Cornices

The recent weather was prime for cornice growth.

Extra caution needed around cornices with current conditions.>

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 6

Persistent Slabs

The Jan.17 layer (down 60-100cm) still shows sudden results and a propensity for propagation in some snowpack tests. 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 7th, 2013 2:00PM