Date of Observation: 11/12/2021
Name: Zach Guy
Zone: Northwest Mountains
Route Description: Traveled on south to east to northeast aspects on Owen to 12,800′
Observed avalanche activity: Yes
Avalanches: A couple of small wind slabs ran today on east aspects above treeline, breaking in just today’s drifted snow. Several large slab avalanches ran off of NE and E aspects of Mt. Owen during the midweek storm. These all appeared to fail on or near the storm interface, about 18″ to 24″ deep. Some of these failed across terrain and in locations that aren’t typical for wind slabs…hinting at our developing persistent slab problem. See photos.
Weather: Strong northwest winds and active blowing snow this morning at all elevations. Winds transport died down this afternoon as scattered clouds developed. No recent precip.
Snowpack: We measured settled storm totals from the midweek storm up to 20″ in sheltered terrain. Significant fresh drifting occurred last night, with new 4F drifts up to 18″ thick. Snow depths on easterly aspects were 4 to 5 feet. We did not observe any signs of instability underfoot apart from some minor localized cracking in fresh drifts. A stability test on an east aspect ATL produced moderate propagating results below a 20″ soft slab, failing in 1mm facets below the 11/9 melt-freeze crust (See photo).
Photos:
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[accordion_item title=”Avalanche Report #1″ parent_id=”my-accordion” open=”false”]Estimated avalanche date: 11/10/2021
Number of Avalanches: 2
Location
Location: Lake Irwin (Robinson Basin, Owen, Ruby)
Location Specific:
Start Zone Elevation: ATL: Above Tree Line
Aspect: NE
Characteristics
Trigger: Natural
Trigger modifier:
Type: Soft Slab
Failure Plane: New/Old interface
Size
Relative Size: R2 small
Destructive Size: D2 – could bury, injure, or kill a person
Avg. crown height (inches): 20
Avg. width (feet): 500
Avg. vertical run (feet): 800
Involvements
# of people caught:
# of partial burials:
# of full burials:
Additional comments: Owen East Bowl
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[accordion_item title=”Avalanche Report #2″ parent_id=”my-accordion” open=”false”]
Estimated avalanche date: 11/10/2021
Number of Avalanches: 1
Location
Location: Lake Irwin (Robinson Basin, Owen, Ruby)
Location Specific:
Start Zone Elevation: ATL: Above Tree Line
Aspect: E
Characteristics
Trigger: Natural
Trigger modifier:
Type: Soft Slab
Failure Plane: New/Old interface
Size
Relative Size: R2 small
Destructive Size: D2 – could bury, injure, or kill a person
Avg. crown height (inches): 18
Avg. width (feet): 300
Avg. vertical run (feet): 1100
Involvements
# of people caught:
# of partial burials:
# of full burials:
Additional comments: Owen East Face
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[accordion_item title=”Avalanche Report #3″ parent_id=”my-accordion” open=”false”]
Estimated avalanche date: 11/10/2021
Number of Avalanches: 1
Location
Location: Lake Irwin (Robinson Basin, Owen, Ruby)
Location Specific:
Start Zone Elevation: ATL: Above Tree Line
Aspect: E
Characteristics
Trigger: Natural
Trigger modifier:
Type: Soft Slab
Failure Plane: New/Old interface
Size
Relative Size: R1 very small
Destructive Size: D1.5
Avg. crown height (inches): 20
Avg. width (feet): 250
Avg. vertical run (feet): 300
Involvements
# of people caught:
# of partial burials:
# of full burials:
Additional comments: Owen/Purple saddle
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[accordion_item title=”Avalanche Report #4″ parent_id=”my-accordion” open=”false”]
Estimated avalanche date: 11/12/2021
Number of Avalanches: 2
Location
Location: Lake Irwin (Robinson Basin, Owen, Ruby)
Location Specific:
Start Zone Elevation: ATL: Above Tree Line
Aspect: E
Characteristics
Trigger: Natural
Trigger modifier:
Type: Soft Slab
Failure Plane: Within storm snow
Size
Relative Size: R1 very small
Destructive Size: D1- Relatively harmless to people
Avg. crown height (inches): 8
Avg. width (feet): 25
Avg. vertical run (feet): 80
Involvements
# of people caught:
# of partial burials:
# of full burials:
Additional comments: wind slabs on Ruby and Owen
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Estimated avalanche date:
Number of Avalanches:
Location
Location:
Location Specific:
Start Zone Elevation:
Aspect:
Characteristics
Trigger:
Trigger modifier:
Type:
Failure Plane:
Size
Relative Size:
Destructive Size:
Avg. crown height (inches):
Avg. width (feet):
Avg. vertical run (feet):
Involvements
# of people caught:
# of partial burials:
# of full burials:
Additional comments:
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