Observation: Turnagain

Location: NW Ridge Magnum

Date:

December 11, 2018 12:00pm

Observer:

Nikki Champion/H. Thamm

Route & General Observations

We toured up the Sunburst up track until crossing Taylor Creek to the South and ascending the NW Ridge of Magnum until 2300′. Intended to evaluate upper elevation band on Magnum, but got deterred by whumping and poor structure at the mid elevations. Dug in several locations to evaluate a melt freeze crust and facet interface.

Two glide cracks noted on Sunburst SW face below weather station.

Red Flags

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Obvious signs of instability

Recent Avalanches?	No
Collapsing (Whumphing)?	Yes
Cracking (Shooting cracks)?	No

Observer Comments

Constant widespread whumping noticed from approx. 2000' to 2300'. Failure upon isolation in hand pits, as well as CTs in the same elevation band. Stability tests show propagation potential. No sign of recent new avalanche activity, but an instability.

Weather & Snow Characteristics

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

Weather

Scatter Clouds
No precip
Calm to Light Winds
Temps in the mid to low 20s, dropping throughout the day

Snow surface

New snow and settled powder from road to high point, increasing as elevation increases. (3"-8" approx.)
Stout melt-freeze crust just under the new snow from the road to 1500'.

Snowpack

Set out looking for a layer of concern throughout the snowpack and at upper elevations. To our surprise, we were able to find a reactive interface at mid-elevations.
Found a consistent melt-freeze crust on the ground beneath the new snow from the road to 2000'.
Above 2000' we found a second melt-freeze crust 1-2" above the basal melt-freeze crust forming angular grains/facets.
New Snow and Settled Powder forming a slab on top of this interface (up to 20")

Hand Pit #1: NW Ridge Magnum - 2050' - NNW Aspect
Failure on Insolation of Hand Pit

Pit #2: NW Ridge Magnum- 2100' - NNW Aspect - HS: 70cm
20" Slab on top of melt-freeze crust/facet interface

Pit #3: NW Ridge Magnum - 2300' - N Aspect - 27 Degree Slope - HS:100 cm BP: 35 cm SP: 20 cm
CT11 down 45 cm on upper MF/facet interface (1mm facets)
CT13 down 45cm on upper MF/facet interface (1mm facets)
ECTP13 down 45cm on upper MF/facet interface (1mm facets)

Pit #4: NW Ridge Magnum - 2300' - N Aspect - 27 Degree Slope - HS: 90cm
CT19 down 45 cm on upper MF/facet interface (1mm facets)
ECTP21 down 45 cm on upper MF/facet interface (1mm facets)
ECTN21 down 45 cm on upper MF/facet interface (1mm facets)

Photos & Video

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