Avalanche Forecast

Issued: Jan 20th, 2014 8:16AM

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

jfloyer, Avalanche Canada

Purcells.

Summary

Confidence

Good

Weather Forecast

This region should stay dry, or else receive very light flurries.Tuesday: Dry. An above freezing layer (inversion) is expected from around 2200-2800m with alpine temperatures reaching around 2C. Ridgetop winds westerly 20-30 km/h.Wednesday: Dry or very light flurries. Light NW'ly winds. Alpine temperatures around -4C.Thursday: Should stay dry. Ridgetop winds light NW'ly. Alpine temperatures around -6C.

Avalanche Summary

On Friday explosives avalanche control produced at least 3 size 3 slab avalanches which failed to ground in steeper alpine terrain. 2 size 3, and 1 size 3.5 natural slab avalanches were also noted. At least 2 of these failed at ground level. All avalanches observed failed on a variety of aspects.On Saturday explosives avalanche control in the Northwest of the region produced a few windslab avalanches to size 1.5 at treeline and in the alpine. No avalanches were reported on Sunday.

Snowpack Summary

Between 60cm and 90cm of well settled storm snow exists as a stubborn hard wind slab in many exposed areas. Thanks to recent warming, steep, sun exposed slopes have seen a daily melt-freeze cycle while surface hoar has been growing in some shaded terrain. Below the recently formed storm slab you may find surface hoar buried around January 8th, although no recent avalanche reports have been attributed to this layer. In the mid to lower pack you may find a surface hoar layer buried in mid December. Further down you may also find the December facet/crust combo. These layers are likely gaining strength, but professional operators are treating them with caution.The biggest concern throughout the region is a layer of weak sugary depth hoar at the base of the snowpack which may coexist with a crust which formed in October. I would continue to be suspicious of any large or unsupported upper elevation slopes, especially if they haven't already avalanched. Possible triggers include a heavy load over a thin spot, a cornice fall or rapid temperature change. Any avalanche failing at this interface would be highly destructive.

Problems

Deep Persistent Slabs

I would continue to be suspicious of any large or unsupported upper elevation slopes, especially if they haven't already avalanched. Although they have become less likely, any deep persistent avalanche would be highly destructive.

Conditions have improved, but be mindful that deep instabilities are still present.>Caution around convexities or areas with a thin or variable snowpack.>Be aware of the potential for full depth avalanches due to deeply buried weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Wind Slabs

Although wind slabs have gained considerable strength, triggering may still be possible in steep, unsupported terrain.

Be aware of the potential for wide propagations due to the presence of hard windslabs.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Jan 21st, 2014 2:00PM