Avalanche Forecast

Issued: Nov 27th, 2016 4:05PM

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

cgarritty, Avalanche Canada

Purcells.

New snow and wind have combined to increase avalanche danger in the mountains. Make conservative terrain choices and post your observations to the MIN.

Summary

Confidence

Weather Forecast

A cooling pattern will develop in the Purcells overnight on Sunday with freezing levels dropping to valley bottom. Winds will remain light and shift to the northwest on Monday. A chance of light flurries is forecasted for Monday with skies clearing overnight and remaining clear on Tuesday.

Avalanche Summary

A lack of field observations is concealing what is expected to be touchy avalanche conditions in the region, especially in the North Purcells. New snowfall and wind has increased concerns for touchy slabs and cornices forming at higher elevations and in exposed terrain.

Snowpack Summary

Up to 40cm of new snow now has seen significant wind effect and has contributed to the touchy cornices and wind slabs forming at treeline and above. The storm snow since Nov 13 has accumulated to 60+cm and has settled into a cohesive slab over the hard November 13 crust. 6mm surface hoar has been observed 10cm below this crust on north aspects at higher elevations and has yielded easy to moderate snowpack test results. Total snowpack depth has exceeded one metre in the North Purcells. The snowpack below treeline is creeping toward threshold for avalanches, but early season hazards such as hidden rocks, stumps, and open creeks remain the primary hazard here.

Problems

Wind Slabs

New snow and wind have been contributing to already touchy wind slabs. Wind loaded features will be easily triggered and have grown in destructive potential.

Travel on ridgetops to avoid wind slabs on slopes below.Avoid areas where the snow feels stiff or 'slabby'.Avoid steep or convex lee features directly below ridgetops.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Storm Slabs

Recent snow has settled into a cohesive slab that may be bonding poorly to a hard crust or surface hoar. Significant loading from new snow and wind has increased the likelihood of triggering deep instabilities.

Carefully assess the bond to the crust before committing to a slope.Use conservative route selection, choose moderate angled and supported terrain with low consequence.New snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Nov 28th, 2016 2:00PM