Avalanche Forecast

Issued: Feb 17th, 2014 9:55AM

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

ghelgeson, Avalanche Canada

Purcells.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Synopsis: Another pacific frontal system passes over the region late Tuesday accompanied by robust SW winds. Freezing levels should drop behind the system as isolated flurries linger in its wake.Tuesday: Freezing Level: 900m; Precip: 2/4mm - 3/6 cm; Wind: Light, SW | Mod/Strong SW at ridgetopTuesday Night: Precip: 4/6mm - 6/10 cm; Wind: Mod SW | Strong/Extreme SW at ridgetop Wednesday: Freezing Level: 700m; Precip: Trace; Wind: Light, West | Strong West at ridgetopThursday: Freezing Level: 700m; Precip: Trace; Wind: Light, SW

Avalanche Summary

An ongoing natural avalanche cycle has tapered ever so slightly but still features natural avalanches to size 3 with control work producing similar results. Skiers and sledders continue to easily trigger avalanches in seemingly benign terrain to size 1. This activity is occurring on all aspects and elevation bands.

Snowpack Summary

The never ending storm has produced 60 - 120 cm of total snowfall across the region which is settling into a cohesive slab that averages 40 - 90 cm in depth. This slab rests on a nasty persistent weak layer (Late Jan/Early Feb.) surface hoar/facet/crust combo that was formed during the month of cold clear weather. Professionals report numerous whumphs and significant propagation potential. Field observations continue to report easily triggered sudden planar failures on this interface in snowpack tests. Natural avalanches have been widespread and destructive. The keyword in Persistent Weak Layer is Persistent, I expect touchy conditions to remain in place longer than we're normally accustomed to due to the pervasive nature of this weakness. Ongoing strong winds out of the SW and W have loaded lee aspects and affected the snow at all elevations, but the affect is most prevalent at and above treeline. More strong winds in the forecast are expected only to add to this problem.Weak basal facets exist in some areas, but triggering has now become unlikely. For the most part, the mid and lower snowpack are strong and well consolidated.

Problems

Storm Slabs

The 40 - 90 cm deep storm slab has mass and some serious bite. You can have a great day in the mountains with a very conservative approach. Watch for any increase in winds, fresh sensitive wind slabs can form surprisingly quickly in open terrain.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Use very conservative route selection, stick to moderate angled terrain with low consequence.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Avoid all avalanche terrain during periods of heavy loading from new snow or wind.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

2 - 5

Valid until: Feb 18th, 2014 2:00PM