Avalanche Forecast

Issued: Dec 28th, 2015 8:01AM

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

triley, Avalanche Canada

South Rockies.

Cold and dry storm snow may take several days to settle and bond to the old surface. Areas with buried facets in the storm snow may cause this problem to persist for longer.

Summary

Confidence

Moderate - Wind speed and direction is uncertain

Weather Forecast

Overcast with light snow overnight and Tuesday resulting in a total of 3-5 cm and light northeast winds. Freezing level will remain at valley bottoms throughout the forecast period. Gradual clearing on Wednesday with light northerly winds. Clear on Thursday with valley cloud as an inversion develops above freezing temperatures in the alpine and traps cooler air in the valleys. The inversion may not develop until Friday.

Avalanche Summary

On Sunday a group of sledders triggered or remotely triggered an avalanche "near" Castle Mountain that resulted in one rider deploying his airbag and being partially buried; the size of the slab avalanche was not reported. See the MIN report for more information. On Saturday, in the east of the region, control work and natural avalanches resulted in wind slab releases up to size 2 on NE facing terrain at 2100m. These fresh wind slabs were failing on the Boxing Day facets. On Friday numerous loose dry avalanches ran naturally to size 1 on east through southeast facing features around 2250m. On Thursday control work produced numerous small loose snow avalanches within the recent storm snow. On Wednesday we received a report of a skier triggered size 1 wind slab on a north aspect at 1800m. It's thought that this avalanche failed on the December 9th melt freeze crust which was down 40cm at the location of the avalanche.

Snowpack Summary

Up to 50cm of storm snow has fallen in the last week. It's been cold and this snow is still quite low density below treeline where it remains unconsolidated. At and above treeline winds from the north and now south/southwest have added a touch of cohesion which has formed fresh wind slabs up to 40cm in depth. These wind slabs rest on a layer of loose faceted snow that is up to 20cm thick. Strong SW winds over a week ago formed cornices that began failing on Boxing day (in the Lizard Range). The mid-December surface hoar may be present down around 50cm on north facing features below treeline. There may be a crust near the bottom of the snowpack from early December below 2100m.

Problems

Wind Slabs

Winds continue to transport loose dry snow that is available into pockets of soft slab in the lee of terrain features in the alpine and at treeline. In some areas these wind slabs may be sitting on a layer of weak facetted snow.

Avoid freshly wind loaded features.>Avoid travelling in areas that have been reverse loaded by winds.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Cornices

Wind combined with loose snow available for transport may have developed new fragile cornice growth.

Extra caution needed around cornices with current conditions.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Dec 29th, 2015 2:00PM