Avalanche Forecast

Issued: Mar 10th, 2014 9:41AM

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

rbuhler, Avalanche Canada

Sea To Sky.

Strong solar radiation and rising temperatures may elevate hazard and could trigger natural avalanche activity on south facing slopes during the day.

Summary

Confidence

Fair

Weather Forecast

A ridge of high pressure will dominate conditions for Tuesday and Wednesday before breaking down on Thursday. There is some wx model uncertainty regarding freezing levelsTuesday: Mostly sunny, freezing level 500-800m overnight, 1300-1500m afternoon, ridgetop winds light W-NWWednesday: A mix of sun and cloud, freezing level 500-1000m overnight, 1500-2000m afternoon, ridgetop winds 20-40 km/h SWThursday: A mix of sun and cloud, freezing level 800-1200m overnight, 1500-1800m afternoon, ridgetop winds light SW

Avalanche Summary

Widespread natural and human-triggered avalanche activity was reported on Sunday.Â This was primarily storm slabs and wind slabs associated with the storm on the weekend.Â Also reported was some wet snow activity at lower elevations where rain occurred.Early reports from Monday suggest less avalanche activity.Â Sluffing is reported from steep, rocky features on solar aspects triggered by the sun.

Snowpack Summary

The weekend storm produced 30-50 cm of dense snow with strong southerly ridgetop winds. The freezing level peaked around 1700 m, meaning low elevation terrain saw significant rain. Expect to find a crust at or near the surface below treeline. The early March melt-freeze crust is now down roughly 90-150 cm. This layer was found on all aspects at treeline and below, and on all but North aspects in the alpine. There are no new snowpack tests on this layer to report, but the continued loading and mild temperatures should help this weakness heal. The mid February crust/facet combo is generally buried quite deep (150 cm+), but there is still some potential for triggering this weakness with large loads in areas with thin or variable snowpack. We're thinking rocky north-facing alpine slopes. Lastly, cornices have grown large during the past few weeks. Give them a wide berth, especially if temperatures are mild or the sun is out.

Problems

Storm Slabs

Weaknesses may exist within or under the recent storm snow. Expect dense wind slabs in exposed Northwest through East facing terrain at and above treeline.

Avoid steep lee and cross-loaded features - typically exposed North and East facing slopes.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 5

Persistent Slabs

There are a couple of melt-freeze crusts buried between 100 and 200 cm deep. It has become much less likely to trigger these, but use caution on steep alpine slopes with thin or variable snow cover.

Avoid thin, rocky or sparsely-treed slopes.>Be aware of the potential for large, deep avalanches.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Cornices

Cornices have grown significantly during the last few storms. They could start breaking off during periods of sunshine or with warm temperatures.

Give cornices a wide berth when travelling on or below ridges.>Cornices become weak with daytime heating. >

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Mar 11th, 2014 2:00PM