Avalanche

Mill City to Pano storm day tour - reactive soft slabs

Steve MaceEastside Region
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Observation photo 1Observation photo 2Observation photo 3Observation photo 4Observation photo 5

Quick report

Cracking
specific
Collapsing
specific

I got out for a quick tour in the Mill City area today to get an idea of new snow totals and the sensitivity of storm instabilities in the area.

  • Today's, new snow seems to be consolidating relatively quickly; however, it was not well bonded to the melt-freeze crust at the new old interface.
  • New snow totals were measured around 40-45 cm (15"-17") at elevations between 8500' and 9500'
  • Surface cracking was observed in areas with recent wind deposits. 
  • Storm instabilities seemed most likely to break at the new old interface. Despite the new snow totals I was not surprised to see no loose dry sluffs during my travels.
-I triggered several cracks and a small storm slab avalanche on steep test slopes near and below treeline. Wind-loaded areas contained fresh slabs ranging in size from 15 cm to 70 cm, most of which were 4f/f. Easy hand sheers and columns failing during isolation. I also noted that even areas with relatively thin wind deposits would break near the surface as well as at the new old interface (a melt-freeze crust from our warm-up this week)

Weather

Air Temp
20
Cloud Cover
overcast
Wind Loading
moderate
Recent Snowfall
40-45
Snow Avail For Transport
large amounts

Heavy snow continued through the morning becoming more intermittent in the afternoon. Winds were moderate to strong BTL with more continuous strong winds near treeline.

Avalanche

-I initiated a D1 storm slab on an NE facing test slope at around 9000'. This slide was approximately 15' wide and ran for about 20'. the crown of this slide was 45cm deep. I would rate the sensitivity as reactive heading towards stubborn. -My photos didn't turn out, but as the cloud cleared out around 430, I observed at least two crown lines along the Sherwin ridge in the typical start zones from the prow to the main AVY path. I would suspect these were D1-1.5 wind slabs.