Holiday crust sandwich

Location Name: 
Forecaster Observation -Northern Swan Range
Observation date: 
Tuesday, December 31, 2019 - 16:30

Is this an Avalanche Observation: 
Yes
Observation made by: Forecaster

Location

Tabs

Quick Observation

Quick tour in the Swan to document surface conditions and monitor the arrival of the storm.

  • Last night’s freezing rain event crusted all aspects and elevations with a 3 to 5 mm breakable crust. This thin rain crust is sandwiching low density snow above the Christmas Eve crust, which is a thicker and stronger crust. The snow was bonding poorly above and below the new rain crust, evidenced by clean shears and shallow cracking. No surface hoar found. 
  • Despite strong winds, there wasn’t much snow available for transport yet. The rain crust capped all but the couple of inches that fell today. There were periods of moderate blowing snow. Drifts were only a few inches thick this afternoon. 
  • Snowfall started around noon, with moderate snowfall rates through the day and 2”-3” of new by 4 pm.
  • We triggered a few harmless sluffs in steep terrain.
Snowpack, Avalanche, Weather Images: 
Travel Details
Region: 
Swan Range - East Side (Hungry Horse Reservoir access)
Route Description: 

To 7,000'

Activity: 
Skiing
Snowpack Details
Snowpack and Weather Details: 
Hide Terrain
Elevation of observation: 
5000-6500 ft
Above 6500 ft
Aspect(s) of observation: 
E
SE
S
SW
Red Flags: 
Blowing snow
Persistent Weak Layers: 
Not observed
New Snow in the past 24 hours: 
2.00in.
Blowing Snow: 
Moderate
Wind Speed: 
Strong (Whole trees in motion)
Wind Direction: 
Southwest
Air temperature: 
Below Freezing
Snow line: 
3000
Sky Cover: 
Overcast (OVC)
Highest Precipitation Rate: 
Moderate Snowfall (S2)
Avalanche Details
Avalanche Details: 
Date and Time of Avalanche: 
Tuesday, December 31, 2019 - 14:30
Number of avalanches: 
2
Avalanche Type: 
Loose Dry/ Sluff
Failure Plane/Weak Layer: 
New/old snow interface
Hide Trigger
Trigger: 
skier
Trigger Modifier: 
Intentionally Triggered
Hide Terrain
Start Zone Slope Angle: 
39
Aspect: 
East
Starting Elevation: 
above-treeline
Hide Size
Destructive Size: 
D1 Relatively harmless to people.
Relative Size: 
R1 Very Small
Crown Height: 
Less than 1 ft
Avalanche Length (Vertical Run): 
300ft.
Avalanche Location: