Northern San Juan

Snowpack

Ann Mellick · Feb 23, 2013 · Northern San Juan

Weather

This morning's mostly clear skies quickly transitioned to overcast, then to S2 snowfall by 10:30 am. Cool temperatures and steady westerly winds (10 mph below tl). 2" of snow accumulated by 1:30 pm.

Snowpack

We dug two pits- one on a southeast and one on a more easterly slope, both below treeline. The SE pit (HS 90cm) reveled a fairly strong melt/freeze basal snowpack with weaker snow, crusts and new snow above. The weakest layer was ~30cm down at the interface of the new snow and a 2 cm mf crust. This interface failed fast and clean in pit tests (CT 2, Q1). However, we felt it could hold a bit of a load despite this (much stronger if crust was not isolated). Failure is most likely to occur at the crust/new snow interface. Upper snow (new) was not slabby. The easterly pit (HS 125cm) revealed and overall weaker snowpack: depth hoar made up the basal 50 cm, a stout midpack in between and new snow on top, with some crusts thrown into the mix. Two failure planes of note: one at a crust/new snow interface ~30cm down and one where the midwinter slab was sitting on old DH. This was the scarier of the interfaces (CT22 Q1 x2). A slab triggered in the upper snowpack would likely step down to the ground. Lower probability, but higher consequence.