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Observations

Region: Turnagain
Location: Magnum - PMS Bowl
Observer:
Date:

Route & General Observations

Toured up through hemlock and alder from the Cornbiscuit pullout. Traversed north below Cornbiscuit, and ascended PMS bowl to 3100′. Our goals were to a) catalog the depth and character of the slab at all elevation bands, b) inventory what has / has not already avalanched on Cornbiscuit and Magnum, c) observe the distribution and reactivity of wind slabs, d) characterize the deep slab problem above 3,000′, and e) look at the structure in an area that has already avalanched during the early December storm cycle.

Red Flags

Observer Comments

No red flags observed. One of the goals of today's tour was to catalog what has not yet avalanched on Magnum and Cornbiscuit. Superbowl, Corner Pocket, the SW face / shoulder of Cornbiscuit, and the large middle chute on the north side of Cornbiscuit do not appear to have avalanched in the early December storm cycle.

Weather

Weather

0930: Cornbiscuit pullout - 800', 3 degrees F, calm wind, clear skies.
1400: Magnum PMS bowl - 3100', temps in the upper teens, calm to light wind, clear skies.
1530: Cornbiscuit pullout - 800', 6 degrees F, calm wind, clear skies.

Snow Characteristics

Snow surface

All elevation bands had surface hoar, increasing in size with elevation from 3-4mm at the road to 6-8mm at 3100'. The snow below the surface hoar varied dramatically: 3-4" of faceted powder on a post-holey breakable wind crust in low elevation alder meadows, 3-4" of faceted powder on a supportable wind crust (5-6" thick) around treeline, and dust-on-crust over supportable slide-for-life wind slab (5-6" thick) in the alpine.

Snowpack

We focused our observations on three areas:

North aspect of Cornbiscuit, ~2000'. Height of snow in the area ranged from 65-80cm (25-31"). We dug a quick pit (HS=65cm) and found 3mm surface hoar over ~10cm F+ faceted powder, over 45cm K hard melt freeze crust, over 10cm 2mm basal facets. No reactive stability test results. (See photo below.)

WNW aspect of Cornbiscuit, ~2100'. We dug a pit in the slide path of one of the Cornbiscuit avalanches that released naturally on December 11th. The snowpack in this location was extremely thin and showed a poor, mostly faceted structure. (See photo below).

SW aspect of PMS bowl, 3100'. Height of snow averaged 100cm. We dug a pit in a shallow spot in order to understand how reactive the Thanksgiving facets are and the character of the slab. Melt freeze crusts in the mid-pack at this elevation are much thinner than at lower elevations (2cm at the most). We found poor structure, moderate to high strength, and propagation potential. (See photo and diagram below.)

Photos & Video

Photos



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