Valanga

Essex/Snowshed area

Michael ReavisFlathead Range & Glacier NP
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Quick report

Cracking
specific
Collapsing
specific

Varying snow surfaces and conditions had us on our toes most of the day from top-to-bottom. Observations and hand pits were key in revealing buried, persistent weak layers throughout most of the terrain we travelled. We mitigated the risk by sticking to ridglines and avoiding avalanche prone terrain. 

•Hiked to 5000' then skinned on an isothermal, thin snowpack. 
•At 5700', 2-4" of recent snow was glopping to our saturated skins. 
•Above 5700', recent snow was dry on shaded aspects, but transitioning on solars and forming a thin melt-freeze crust which was felt on the descent. Trees were dripping to our high point of 7400'. 

•We experienced aubible collapses around 6200'. Cracking was minimal and limited to underfoot. 
•We dug a small pit at 7000' on an E aspect to assess the upper snowpack for the buried surface hoar layer, which we found. Shoveling the pit triggered large rollerballs (see photo)
•The buried surface hoar was capped with an 8-12" 1F-hard slab (peristent slab problem confirmed).  (see photo)
•We observed recent, natural slab avalanches (D2-D3) on S aspects at upper elevations, mainly confined to the Paola Drainage. One slide in particular appeared to have "stepped down" to weaker layers. (see photos)

•We closed off most terrain because the solars were rollerballing (moistening) and there was a persistent weak layer/slab lurking in the shaded/sheltered. 
•On the descent, we skirted the top of a large, avalanche prone slope (~38*) and triggered a large D 2.5 avalanche that broke 1000ft wide and ran to the flat 700ft below. (see photos) This slide failed on buried surface hoar. 

•Skiing was predictable and safe above 6500' on ridgeline. Below was wet and manky. 


Audible whumphs and cracking starting at 6200' at ridgeline.

Weather

Air Temp
Above freezing (all elevations)
Cloud Cover
scattered
Wind Loading
none
Snow Avail For Transport
none

Brief, moderate gusts from the W and an upper level cloud layer shading out terrain in isolated locations.

Avalanche

Size
D3
Type
HS
Count
4
Aspect
SE
Trigger
N
Elevation
7000 ft