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Alpine conditions

Location Name
North Sister
Region
Three Sisters Area
Name
Kevin Grove
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Position
COAC Observer
Date and time of avalanche (best estimate if unknown)
Red Flags
Recent avalanche activity
Avalanche Type
Slab
Trigger type
Natural
Slope
45degrees
Aspect
Northeast
Elevation
8000ft.
Crown Height
1 ft
More detailed information about the weather

 The air temp was 2c and snow temp was -3c.  Skies were overcast and winds started calm but grew stronger around 11am before calmiing again.

More detailed information about the avalanche

 I toured into North Sister today to check out the conditions in the high alpine.  The road is clear to the pole creek TH.  We hiked on dirt and firm snow for 30 minutes before starting to skin.  The snow was frozen melt-freeze crust that totally supported our weight of skis and boots to 7000ft.  Approaching the NE face, just above treeline, my partner noticed a crown in the Early Morning Couloir (see photo).  It appeared to be a 1-2ft natural release and quite sizable.  We continued to tour over to the east face and approaced a SE facing slope low on the east buttress.  Initially at 7500ft we encountered 2 inches of wind slab over the top of two small rain crusts that sat on 12 inches of low density (4F) snow on top of a firm ice layer.  Further up the slope and approaching more of a gully we found a deeper snow pack up to 3 feet above the ice layer consisting of the same shallow wind slab, ice layers, 4F snow, then a very thin ice layer on top of 1F snow transitioning to pencil hardness about 1 foot above the ice layer.The top wind slab and ice layers failed very easilty on both hand shear and compression test.  Another moderate failure occured on the compression test at the very thin ice layer lower down.Be safe out there.Kevin