Date of Observation: 04/09/2023
Name: Zach Guy
Zone: Northwest Mountains
Route Description: Rec tour this morning on Purple Peak, traveling on southerly an northeast aspects up to 12,800′
Observed avalanche activity: Yes
Avalanches: Two new alpine cornice falls since I was last in this area on the afternoon of 4/7 (D1.5 and D3) and a recent glide avalanche off of rocks on West Beckwith (D1.5)
Weather: Mid-level clouds passed overhead a few times but still lots of solar input. Light winds.
Snowpack: High northerly aspects held dry, stable powder. Surfaces were well-frozen this morning at all elevations. By 11:30 a.m., rollerballs and pinwheels started coming off of rock bands on east aspects NTL as the top few inches got wet. Good corn skiing at that time on southeast NTL. Above treeline south has only seen meltwater go a few inches deep during the last few days. On below treeline south, there were timber sled tracks sinking in about 10″.
Photos:
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A small cornice fall off of Purple (on the right) next to a larger one that ran a few days earlier.
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Very large cornice fall off of Scarp Ridge (bottom left). The other was observed a few days ago. Note how the cornice in the foreground is overhung about 30 feet, and you wouldn’t know you were standing above air if you were on it.
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A small glide release on West Beckwith.
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A large glide avalanche in the Raggeds (outside of our forecast area)
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These rollerballs and pinwheels started happening around 11:30 a.m. East aspect, 11,200′.
Estimated avalanche date: 04/07/2023
Number of Avalanches: 1
Location
Location: Lake Irwin (Robinson Basin, Owen, Ruby)
Location Specific:
Start Zone Elevation: ATL: Above Tree Line
Aspect: S
Characteristics
Trigger: Natural
Trigger modifier:
Type: Cornice
Failure Plane:
Size
Relative Size: R1 very small
Destructive Size: D1.5
Avg. crown height (inches):
Avg. width (feet):
Avg. vertical run (feet):
Involvements
# of people caught:
# of partial burials:
# of full burials:
Additional comments: Purple Peak. This is new since 4 p.m. on 4/7, but it entrained some wet snow so I’m guessing it ran later that afternoon.
Estimated avalanche date: 04/08/2023
Number of Avalanches: 1
Location
Location: Oh-Be-Joyful Basin
Location Specific:
Start Zone Elevation: ATL: Above Tree Line
Aspect: N
Characteristics
Trigger: Natural
Trigger modifier:
Type: Cornice
Failure Plane:
Size
Relative Size:
Destructive Size: D3 – could destroy a car, wood-frame house, or snap trees
Avg. crown height (inches):
Avg. width (feet):
Avg. vertical run (feet):
Involvements
# of people caught:
# of partial burials:
# of full burials:
Additional comments: Scarp Ridge above Blue Lake. New since 4/7. Failure date estimated.
Estimated avalanche date: 04/07/2023
Number of Avalanches: 1
Location
Location: Beckwith Range
Location Specific:
Start Zone Elevation: ATL: Above Tree Line
Aspect: E
Characteristics
Trigger:
Trigger modifier:
Type: Glide
Failure Plane: Ground
Size
Relative Size: R1 very small
Destructive Size: D1.5
Avg. crown height (inches):
Avg. width (feet):
Avg. vertical run (feet):
Involvements
# of people caught:
# of partial burials:
# of full burials:
Additional comments: New since 4/6. Failure date estimated.
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