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Avalanche: Summit

Location: Manitoba

Date:
Observer:
Route & General Observations

Skied from top of Manitoba in very impressive, full-strastrugi conditions. Wind effect was variable ranging from impenetrable to breakable on most of the face with mostly powder (some wind affected areas) below tree and alder line.

Avalanche Details
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Trigger NaturalAvalanche Type Unknown
Aspect EastElevation 2500ft
Slope AngleunknownCrown Depthunknown
WidthunknownVertical Rununknown
Avalanche Details

Small (D1 or D2) natural avalanche that likely broke during the wind storm yesterday seen across the road from Manitoba on Fresno Ridge.

Red Flags
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Obvious signs of instability
Recent Avalanches?Yes
Collapsing (Whumphing)?No
Cracking (Shooting cracks)?No
Observer Comments

Several natural avalanches seen in Summit, including the slide on Fresno Ridge and the slides noted by Heather Thamm yesterday that broke during high winds. Cracking around skis on the wind slabs but no shooting cracks or whumphing no matter how hard we tried, and how often we set our own skin track.

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

Parking Lot @ 10:30 am - Cloudy, no precip, no winds
Treeline @ 12 pm - Overcast, no precip, steady and light winds
Alpine @ 1:30 pm - Broken Clouds with sunshine moving in, no precip, no wind.

Snow surface

Below Treeline - snow covered in pine needles from the wind, soft settled powder.
Treeline - right when you pop out of the narrow uptrack in the trees there is wind affected snow and softer strastrugi. A bit further up on the flatter slopes at treeline and right above treeline the snow is settled powder.
Above Treeline - Impressively wind affected! Variable SASTRUGI, ranging from thin (2 inch) to thick (1-2 ft) wind slabs that ranged from pencil hard to 4 finger and boilerplate impenetrable to breakable. Some places were reminiscent of ocean waves frozen in space, about to break. There were spots we wish we had brought ski crampons while skinning near the southern ridge on Manitoba. The whole west face of Manitoba was wind affected sastrugi. We did find one nice strip of powder down the gully in the center.

Cross loading on Fresno Ridge.

Snowpack

We dug several hand pits and probed with our poles along the way. Basically everywhere above treeline we found the following structure:

Wind slabs ranging from F+ to 1F over
F hard facets over
Older P hard wind slab with P hard crusts in some places that were pencil thick over
F hard depth hoar to the ground

The hand pits required medium to hard effort to budge the top wind slab.

Photos & Video
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