Avalanche Forecast
Issued: Feb 19th, 2014 9:58AM
The alpine rating is Storm Slabs and Persistent Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeWe're moving from a storm slab problem to a persistent slab problem. Check out this blog post for thoughts on the current situation and strategies for the next the chapter.
Summary
Confidence
Fair - Forecast snowfall amounts are uncertain on Thursday
Weather Forecast
Synopsis: The last of the heavy hitting storms has left the province. A quick hitting pulse racing down from the NW will cross through the region Thursday leaving some very light density snow in its convective wake. A serious eastern pacific ridge brings clearing skies this weekend. Too early to say how long its reign will last. Thursday: Freezing Level: 700m; Precip: 6/12mm - 6/20 cm; Wind: Light, SW | Extreme SW at ridgetop.Friday: Freezing Level: Valley Bottom; Precip: Trace; Wind: Light, NW | Mod W/NW at ridgetopSaturday: Freezing Level: Valley Bottom; Precip: Nil; Wind: Light
Avalanche Summary
The natural avalanche cycle remains quite productive. On Tuesday avalanches to size 2.5 were triggered naturally and accidentally by skiers. This activity is occurring on all aspects and at all elevation bands. One standout incident just south of the region involved a skier skiing next to previously skied terrain. The skier remote triggered a size 1.5 avalanche from 20m away which sympathetically released a second size 1.5 avalanche 50m further away. In a separate incident it sounds like a skier was caught and carried 100m in a size 2.5 avalanche in the southern portion of the region. The skier survived, but sustained injury.I suspect that avalanche activity was widespread and perhaps even a little bigger Wednesday.
Snowpack Summary
The never ending storm cycle has produced 120 - 175 cm of total snowfall across the region which is settling into a cohesive slab that averages a meter 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. Field observations continue to report easily triggered sudden planar failures on this interface in snowpack tests. Large settlements / "whoomphs" have been reported at all elevations, even in previously skied terrain. Large natural avalanches have been widespread and destructive. The persistent weak layer under all the storm snow is incredibly pervasive in the region. I expect touchy conditions to remain in place longer than we're normally accustomed to. Ongoing strong winds out of the SW and W have loaded lee aspects and damaged snow at all elevations, but the effect is most prevalent at and above treeline. More strong winds in the forecast are expected only to add to this problem.For the most part, the mid and lower snowpack are strong and well consolidated.
Problems
Storm Slabs
Previously SW winds should switch to the NW Thursday. With plenty of new storm snow available for transport, fresh sensitive wind slabs will add even more complexity to an already tricky situation on wind exposed terrain features.
Avoid freshly wind loaded features.>Do not travel on slopes that are exposed to cornices overhead.>Avalanches initiated in the most recent storm snow could easily step down and trigger the persistent slab.>
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
This problem is surprising very experienced professionals and remains primed for human triggering. This meter deep slab has shown a propensity for remote triggering, a phenomenon that should become more prevalent as the slab gains cohesion.
Use very conservative route selection, stick to simple well supported terrain that is low consequence and free of overhead hazard.>Avoid all avalanche terrain during periods of heavy loading from new snow or wind>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 20th, 2014 2:00PM