Avalanche: Bobs Knob 3/17/2010

Observer Name: 
Pattereson
Observation Date: 
03/18/2010
Occurrence Date: 
03/17/2010
Occurrence Time: 
Unknown
Region: 
Provo
Provo Canyon
North Fork
Bobs Knob
Location Name: 
Various Provo Mountain Wet Slab Activity
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Avalanche Characteristics
Elevation: 
Unknown
Trigger: 
Natural
Avalanche Type: 
Wet Slab
Weak Layer: 
Depth Hoar
Depth (avg): 
unknown
Width: 
Unknown
Vertical: 
Unknown
General Comments

 This wet slab on Bob's Knob pulled out on St. Patrick's day sometime after 3:00pm.  Also reported by Scott Hart of North Fork Fire.  This one started as a wet loose just below the upper most cliff band and then caused a wet slab to pull out below it.  One common theme to all of these wet slab avalanches that we have seen over the last couple of days is an easterly component, and the rocks and cliff bands playing a part.  Temps between 8'000 and feet and 10'000 remained above freezing, substantially, for 48 hours, likely due to a thermal band of warmer air that existed at this elevation.  The warm temps coupled with the thinner Provo snowpack likely made it easier for the rocks/cliff bands to warm up, radiate heat and cause water to percolate down to the weak basal facets and get things moving.  

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General Comments 2

 The debris from this avalanche also covered up the heavily used trail that people use to access the terrain off of the Alpine Loop Highway.  There was a snowmachine track leading into the debris that looked fresh, as if the rider had been below the slope on the morning of St. Patricks day, before it went natural.  This one started at 8200' on a due East aspect and ran to 7300'.

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General Comments 3

 Southeast facing Mill Canyon peak.  8800' ran down into Bear Canyon around 7000'.  

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General Comments 4

 Below the Gunsight notch of Cascade Cirque.  This one looked like it also was initiated by a wet loose that originated around the cliff bands and then pulled out this wet slab at 9800' running down to the bench above Stewart Falls.  This was on more of an ENE aspect.  

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