Hasty pit on Great Northern, skier triggered small slab

Location Name: Great Northern Observation date: Monday, March 12, 2018 - 12:30	Is this an Avalanche Observation: Yes

Observation made by: Public

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Quick Observation

Toured up Stanton Creek and Stanton Glacier to lower summit of Great Northern. 04:30 start. Summit at 11:00. Highway at 2:30
Unintentionally skier triggered a 4 inch deep slab with a 12 foot wide crown below Grant Ridge at 12:30 on a near 38 degree North-facing slope at about 6800'. This was mid-slope in a wind-sheltered area that was very shaded and cold. The crown broke at the skier's feet and the debris stopped in a band of trees thirty feet below the skier.
Saw no other evidence of natural or human-triggered avalanche activity from 3/11or 3/12 on either shaded or sunny upper elevation slopes in the Stanton drainage before noon.
Observed no cracking or other signs of current instability above 6800'.
Climbed steep East-facing slopes below 6000' before 09:00 that were sun crusted and had rollerballs from 3/11.
Observed D 1.5 debris on the glacier from numerous avalanches that ran 3/9 or 3/10 on the steep, North-facing slopes on Great Northern's north ridge.
One of these slides looks like it crossed the glacier and triggered a 6-10' storm slab on a West-facing slope at about 7500'. The crown was near the top of the small slope and was about 250 feet wide. Debris ran full path, about 200 vertical feet.
Snow surface on North-facing slopes near the Summit showed drift patterns, but the surface snow was fist hard and skied well.
See Snowpack Details for results of hasty pit at 8600'
See pic of glide cracks (filled in by recent snow) on the steep rock slabs above the lake at Stanton Creek's headwaters.

Snowpack, Avalanche, Weather Images:

Travel Details

Region:

Flathead Range - Middle Fork Corridor

Route Description:

Stanton Creek, Stanton Glacier, lower summit of Great Northern. Exit via lakes to East of Great Northern and North and Northwest slopes below Grant Ridge.

Activity:

Skiing

Snowpack Details

Snowpack and Weather Details:

Terrain

Elevation of observation:

3500-5000 ft

5000-6500 ft

Above 6500 ft

Aspect(s) of observation:

Persistent Weak Layers:

On the surface

New Snow in the past 24 hours:

0.00in.

More comments about the snowpack and weather:

Hasty pit near lower summit of Great Northern on 32 degree North-facing slope at 8600'. CT 13 at 30cm from surface, Q3, Fist hard slab CT 17 at 40cm from surface, Q2, four finger hard slab ECTN 16 at 30cm from surface ECTN 22 at 40cm from surface

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