Avalanche

Sherwin ridge - Reactive wind slabs

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

Quick report

Cracking
specific
  • I went for a tour this afternoon to get an idea of snow totals from today's quick-moving storm and to get a read on the wind slab potential.
  • Temperatures were relatively warm this morning but dropped quickly as the storm rolled in, keeping the snow loose and unconsolidated, largely right side up.
  • In areas with smaller amounts of storm snow, skinning proved to be a bit challenging with a "dust on crust" vibe. However, I never found myself wishing for ski crampons.
  • Today's winds were largely moderate to strong, and they proved productive at transporting snow in exposed areas near and above treeline.  As the storm cleared out around 3-3:30 this afternoon the winds continued to transport snow along the ridge.      

Signs of Instability:

  • I managed to trigger a couple of Loose Dry avalanches today on small, steep test slopes in the loose and unconsolidated storm snow near and below treeline.
  • Shooting cracks were easy to initiate in wind-loaded terrain.
  • I saw two natural avalanches and intentionally triggered several windslab avalanches along the Sherwin ridge.  Crown depths ranged from about 8"-2' deep. The largest avalanche I triggered along the ridge initiated from approximately 5' away and propagated about 30 meters wide. 

Weather

Air Temp
23
Cloud Cover
overcast
Wind Loading
moderate
Recent Snowfall
15-25
Snow Avail For Transport
moderate amounts

Snow started in the Mammoth Area with flurries around 9:00 am, with rates increasing after 10:00 AM. Peak snowfall impacted the area from 10:00-15:00, with periods of snowfall over 1" per hour. Storm totals approx 15 cm-25 cm depending on elevation. Wind speeds dropped throughout the storm from mostly strong speeds to more modeate speeds during my tour.

Avalanche

Size
D1
Type
L
Count
3
Aspect
NE
Trigger
AS
Elevation
9000 ft

Small loose dry avalanche triggered on steep test slope below treeline.