Avalanche

Doris Ridge

Guy Zoellner/Lydia WilloughbySwan Range
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Observation photo 1Observation photo 2Observation photo 3Observation photo 4Observation photo 5

Quick report

Cracking
specific

We headed into the northern Swan range to assess wind activity and the wind slab problem while continuing to look for any signs of instability of the weak layer that formed New Year's week.

  • Taking advantage of decent visibility in the morning, we spotted one small, recent avalanche at upper elevation. Other signs of instability included shooting cracks and reactive wind slabs on test slopes (both isolated). 
  • Wind slabs were up to 1F hardness and 5" thick, and rapidly developing on leeward slopes. We were surprised to find that most of these slabs were stubborn with only localized cracking. In this location there would be a high possibility of finding small wind slabs 150' below ridgelines.
  • New snow amounts were 5" in mid elevations and 3" at lower elevations by 1500!!
  • Topped over SH was most evident on an easterly aspect at 40cm down and we found it to be non-reactive in this location.  There was a 1" rain crust (from Sunday) up to 6100, beneath the new snow. 
  • We received propagating results (ECTP28) on facets above the Christmas Crust on a sheltered, northerly slope.

This area is a popular area for sledders to get lured off the ridge and romp in some steep, relatively open terrain. While inviting, with the wind slab problem we noticed today, riding and side-hilling in these wind-loaded start zones above terrain traps may have ended with consequences.

One recent D1 (small) avalanche on at upper elevations on a northerly slope in wind-loaded and exposed terrain.

Weather

Air Temp
30
Cloud Cover
overcast
Wind Loading
intense
Rain Elevation
3000
Recent Snowfall
7
Snow Avail For Transport
small smounts

Snow started at 11:00 and continued at S-1 for the afternoon. Strong winds were transporting snow most of the day, as the winds shifted from easterly to southwesterly.

Snowpack

  • HS = 175cm  / N / 6400' / 37°
      • ECTP28 down 60cm on facets above the Christmas Crust and non-propagating results on preserved graupel and new snow interfaces at moderate taps. Right side up snowpack above the Christmas Crust.
  • HS = 220cm / N / 6600' / 30 °
    • 2 x ECTX
    • In this sheltered, but recently wind affected location, we did not find evidence of surface hoar. 
  • HS = 190cm / E /6450' / 25°
    • 40cm down we found minimal flattened and decomposing surface hoar flakes up to 12mm, CTN.

Avalanche

Size
D1 R1
Type
SS
Aspect
N
Trigger
N
Elevation
6700 ft

Wind-loaded, burned terrain with a northerly aspect. Viewed through binoculars.