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"Slip Sliding Away"
Location Name:
Roof of the Swan
Observation date:
Tuesday, April 7, 2020 - 13:00
Is this an Avalanche Observation:
Yes
Observation made by:
Public
Location
Tabs
Quick Observation
Traveled to the Bob Marshall Wilderness to camp out for a few nights, enjoy the full moon, and try to escape the hot temps in the valley by climbing to the height of the Swan.
We stayed safe by traveling in pre-dawn hours and avoiding exposure to avalanche terrain in the afternoon.
We observed numerous large avlanches on 4/07/20 (up to size 3). These slides appeared to be wind slabs triggered naturally by cornice falls and warming near rocky areas. All of the slides were on East facing terrain. The largest slide we observed appeared to step down to a persistent weak layer (March 24?). We believed that they failed on sunday or monday 4/5 or 4/6.
Tuesday evening, the snow was still dry and powdery on northern aspects and also on high elevation westernlys due to aggressive winds from the west keeping the surface temps low. We observed beatiful wind loading illuminated by evening light blasting over the Swan Crest.
On Wednesday and Thursday, winds were more calm however east facing slopes above 7500' remained safe to ski until 1130am. By noon, East facing and South Facing we saturated enough to cause instabilities.
As we made our way back down to the Valley yesterday (4/9), we found that sheltered north facing terrain still harbored some dry powdery snow down to 6500'. Below 5500' did not seem to have a refreeze at all wednesday night (4/8).
Snowpack, Avalanche, Weather Images:
Snowpack, Avalanche, Weather Videos:
Wind Loading or Northern Lights?
Video of Wind Loading or Northern Lights?
Travel Details
Region:
Swan Range - South (south of Swan Lake)
Snowpack Details
Snowpack and Weather Details:
Red Flags:
Avalanches from the past 2 days
Blowing snow
Rapid or prolonged warming
Rollerballs / pinwheels
Persistent Weak Layers:
Buried
Avalanche Details
Avalanche Details:
Date and Time of Avalanche:
Monday, April 6, 2020 - 12:00
Number of avalanches:
2
Avalanche Type:
Soft Slab
Failure Plane/Weak Layer:
New/old snow interface
Trigger
Trigger:
natural
Trigger Modifier:
Cornice Fall Triggered
Avalanche Location:
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