Sheep Creek Drainage

We traveled on North, Northwest, and East aspects today with two goals.  1. To get a look around the higher peaks for avalanche activity.  2. Target shallow snowpack areas looking for the persistent slab avalanche problem.  We came up short on any significant avalanche activity, although there were some minor wet loose avalanches and lots of roller balls on East and South aspects below rock and cliff bands.  You could still make out the filled in crown of a large avalanche on Sentinel Peak.  Impressive.  We dug a pit on a NW aspect at 7700' and found poor snowpack structure with alarming snowpack test results.  See Snowpack obs section for more details.  I was surprised to not see more natural wet loose activity, but by 1300 when we skied a NW aspect, we found some warming snow and rollerballs releasing from our skis.  I would expect the wet loose action will intensify this weekend with strong solar input and continued warm temperatures.  We found plenty of wind slab formation on exposed upper elevation ridgelines from previous North and Northwest winds, but none were reactive.  

Many of us are used to stabilizing avalanche conditions by this time in the year, especially when thinking about deeply buried persistent weak layers.  That is not the case right now.  There are places where the snowpack is deep and stable, but there is a lot of variability out there.  Keep an eye on the 2/1 Rain Crust that can be found anywhere from 60-90 cm/2-3' deep.  In some places this is well bonded, in others there remains weak snow above, below, or between the crusts.  I haven't found any buried Surface Hoar in my last couple days of travel, but be on the lookout for it in shady protected areas.  My biggest surprise today was the reactivity of the basal facets in my snowpit.  When you have uncertainty in the snowpack, choose terrain that won't avalanche (less than 30 degrees).  

In a snowpit at 7700' on a NW aspect, we found 135 cm/53" of snow.   We found a wind-stiffened layer on the surface and a layer of 3-4mm graupel 45cm/18" down.  A knife-hard crust was found 90 cm/3' from the surface with some weaker snow around the crust.  The most alarming part of the snowpit was the very weak 4F hard basal facets and depth hoar that were below a Pencil hard Melt Freeze Crust found around 110cm/3.5' from the surface.  We conducted a Compression Test, Extended Column Test, and a Propagation Saw Test all with results that gave me pause.  CT21SC down 110cm, ECTP17 down 110cm, and PST37/100END on the Basal Facets at 110cm down.