First, WAC was astounded at the fabulous turnout at the Avalanche Awareness Seminar held Tuesday evening at the Joseph Community Center. Clyde Raymer, President of the Eagle Cap Extreme (ECX) sled-dog race officially counted 91 fully engaged participants. WAC also thanks John Groom, Director of the Payette Avalanche Center for conducting this amazing seminar and Clyde along with the entire ECX folks for the kind donation of space to host the event.
We will have our normal full-up weekly summary report available on Sunday. Julian and Keith (stationed out on the course) are busy conducting avalanche hazard evaluation for and performing On-Call Search and Rescue duties throughout the ECX event.
Bottom Line Southern Wallowas: (Courtesy our senior advisor Don Sharaf)
Warm temperatures and little new snowfall in the past week have given the snowpack time to stabilize. The only layers of concern currently is the recent windslabs deposited on north and east aspects from strong winds on Sunday night (1/10evening-1/11am). These slabs spontaneously released in high angle leeward terrain during deposition and might be triggered by travelers in alpine terrain. Additional, possibly sensitive wind slabs from the Tuesday/Wednesday event bears careful evaluation.
Recent Activity: On January 6 and 7 warm temperatures and clear skies produced a widespread avalanche cycle on south aspects between 5500’ and 7500’. Some of these wet loose slides scoured a foot (30cm) deep into the snowpack creating avalanches big enough to bury several people. (WL-N-D2-I).
Strong SW winds overnight on January 10 created relatively shallow winds slabs that naturally released on high angle (>45 degrees) easterly aspects between 6000’ and 7000’. (SS-N-D1.5-I)
No collapsing, or shooting cracks, were observed on any aspects in the past four days (1/8 to 1/11, 2010).
Concern #1: Shallow wind slabs (estimated one foot/30cm deep at most). Warm (above freezing) temperatures should cause these rapidly deposited slabs to gain strength fairly rapidly. Lingering sensitivity of these slabs may linger in deeper deposits near ridgecrests in the true alpine zone (above 8000’) or in very steep (>45 degree) terrain.
Concern #2: Although buried surface hoar (feather-like frost crystals that form on the surface and then can be buried by subsequent snowfall) lingers in the snowpack (between 16” and 24”/45-60cm deep) it has appeared to gain strength and has low propagation potential. Several pits showed planar, but sluggish shears (Q2) on that buried surface hoar layer, but showed no propagation with the Extended Column Test.
Buried Surface Hoar is generally considered “Guilty – until proven innocent.”
In a large number of test pits dug on all aspects in the Norway Creek, Pine Creek, Granite Creek, and Blue Creek drainages (more than a dozen pits) the surface hoar ended up free of charges, only one pit showed that it should remain on probation.
Bottom Line Northern Wallowas: (Courtesy Keith and John Groom)
Several outings this past week noted continued strengthening of the lower (nearest ground level) weaknesses in the snow pack due to the continued warm weather. Recent moist new snowfall occurring Tuesday and into Wednesday morning yielded 2” up to 8” from about 5500’ to 8000’ respectively. There have been no reports of natural avalanches with this new snow and field work of ours has not produced any human triggered activity of note. After hard work we were able to get a very small slide on a test slope (N aspect 8000’ 36 degrees) to release at the new snow / old snow interface. Hard work means two cornice cuts/drops and two ski cuts, releasing on the second. In places it stepped down to just below the new/old snow interface to underneath a 2” older wind slab. Occasional spotty collapsing and whumpfing was noted after this new snow event but generally on flatter terrain.
Concern #1: Wind Slabs and drifts. With strong S -> SW winds early in the week and during the storm there are some fairly deep wind slabs on north through easterly aspects. These are areas where we saw movement of the new snow when given a pretty strong nudge. Cornices have grown more with this new snow and we are now giving them a wider berth when traveling on ridges. Steep chutes (35 degrees +) and couloirs seem to have captured a lot of this new snow.
Concern #2: Buried surface hoar and facet layers. On one test slope near a creek bottom easy hand shears produced a noticeable weakness at a probable surface hoar deposit under this new snow. With the warmth we’ve had, this appears to be likely only on the most northerly shaded open terrain. Lastly, the more deeply buried loose granular snow, although strengthening now, could still be problematic where a thin snow cover exists. Just this past week on Wing Ridge, extended column test results show the propensity for propagation on this weak sugary layer nearest the ground.
This new snow was welcome and has helped to cover the rain crust yuckiness in many places. This is providing a much nicer skiing experience where our observers above were skiing terrain and traveling about this week in terrain up to 35 degrees with only heightened avalanche condition awareness and with consideration given to the concerns above.