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Observation: Summit

Location: Tenderfoot

Date:
Observer:
Route & General Observations

Ascended to 3400′ on Tenderfoot Ridge and descended a SW aspect. We were on the hunt for slabs and looking at surface conditions, as well as the reactivity of persistent weak layers in starting zones.

 


The snow was soft where we dug on a SW aspect, but further along the ridgeline we found hard wind slab and breakable wind crusts

 

Snow pit revealed weak basal facets and the Jan. 21 BSH under 4F hard snow. In other leeward areas slabs may be present sitting over these persistent weak layers.

 

Section of 4 inch thick wind slab that broke off while skinning and slid easily on the surface below

 

Wind has scoured away the snowpack on northerly aspects on the skin track in places down to the old melt freeze crust

 

A new crop of surface hoar is growing at all elevations and is found on a variety of surfaces above treeline, including hard windslab, faceting sastrugi, breakable wind crust, settled snow, and decomposing melt freeze crust

Red Flags
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Observer Comments

None.

Weather & Snow Characteristics
Please provide details to help us determine the weather and snowpack during the time this observation took place.
Weather

1100 at 1400': -6 degrees, clear, calm, no precipitation
1140 at 2480': clear, light winds, no precipitation
1400 at 3200': clear, single digits, light winds, no precipitation
1445 at 1400': 9 degrees, clear, calm, no precipitation

Snow surface

1400'-2000': 1 cm of surface hoar over 4" of near surface facets over a stout melt freeze crust
2000'-2500': 1 cm of surface hoar over 5" of near surface facets over a decomposing, breakable melt freeze crust
2500'-3300': 5mm of surface hoar sitting over either: melt freeze crust (in scoured areas), faceting sastrugi, hard and stout wind slab, 1-2" wind crust, or settled powder from the last storm that is faceting.

Of note, the surface snow is much more consistently wind affected in Summit Pass above treeline, than what we have seen in Turnagain Pass from the Jan. 26 storm.

Snowpack

Above treeline along the uptrack along the NW ridge, the Northern aspects were highly wind affected from last week's winds - scoured areas intermixed with very hard wind drifts and slabs. SW aspects were wind loaded just off ridgelines and cross loaded in gullies. Probing along the ridgeline we found variable depths ranging from 30 cm in more scoured areas along the ridge to 250 cm in more wind loaded areas on SW aspects.

At 3200' on a SW aspect we dug well below ridgeline in a thinner spot (80 cm) where we felt basal facets near the ground while probing. Shovel tilt failed easy/mod after 7 taps on the Jan. 21 BSH, 15cm down from surface. Shovel shear below that failed under moderate force on basal facets above a basal ice layer. CT 6 down 15 cm on the Jan. 21 buried surface hoar. ECTX.

Further along the ridgeline at ~3400 on a SW aspect we found much harder wind affected snow where a wind slab could be sitting on a persistent weak layer. Probing revealed everything from a few inch wind crust over facets to a more homogeneous wind slab.

Photos & Video
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