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Small Wind Slab Avalanche, Middle Peak, Castle Lake

Location Name: 
Castle Lake
Castle Lake
Date and time of observation: 
Mon, 02/15/2021 - 11:30am
Observation made by: 
Red Flags:
Recent avalanche activity
Whumphing noises, shooting cracks, or collapsing
Recent loading by new snow, wind, or rain
Rapid warming

Location Map

96067 Mount Shasta , CA
United States
41° 13' 11.1072" N, 122° 23' 0.9168" W
California US

Snowpack Observations


We triggered a small avalanche on a test slope by cornice fall today. The result was a small wind slab avalanche. It was approximately 20 feet wide and 20 feet long. The bed surface was a thin icy crust. The crust was 12 inches deep in a pit we had dug earlier. Temperatures were warming up and snow surfaces were beginning to feel moist and heavy. The trees were dripping melting snow. 

  • Observation Location: Castle Lake
  • Elevation: 6200 Feet
  • Date: 20210215
  • Time: 1130
  • Observer: Ryan and Aaron
  • Sky Conditions: Scattered (SCT) - Periods of fog and scattered clouds at various altitudes.
  • Current Precipitation: NO 
  • Air Temperature:  39 °F
  • Surface Penetration: Ski penetration (PS) = 6 in (15 cm), boot penetration (PF) = 12 in (30 cm)
  • Total Snow Depth (HS): 80 in (205 cm)
  • 24-hour New Snow Depth (HN24): 3 in (8 cm)
  • 24-hour New Snow Water Equivalent (HN24W): 0.35in (8 mm)
  • Wind Direction: SW 
  • Wind Speed:Light (L), 1-16 mi/hr, twigs in motion 
  • Column & Block Tests:
    • Slope Angle & Aspect: 40º, NE - test slope. 30º NE- snow pit
    • ECTX
    • CT13 SC  ↓ 12 in (32 cm)
    • Avalanche: SS-AC-R1-D1



  • ECTX
  • Middle Peak, Castle Lake
  • Left Peak, Castle Lake
  • Fog
  • A small SS-AC-R1-D1 avalanche Middle Peak, Castle Lake

Weather Observations


Snow shower continued until 9 a.m. Fog would move in and out with scattered clouds as we toured up to Middle Peak. Temperatures were rising. A high of 43.5 ºF was recorded at 1 p.m. at our Castle Lake weather station. Roller balls and pinwheels were forming on south aspects. It would have been a perfect day to build a snowman. Moist packable snow was everywhere. 


Cloud Cover: 
50% of the sky covered by clouds
Blowing Snow: 
Accumulation rate: 
Air temperature: 
Above Freezing
Air temperature trend: 
Wind Speed: 
Wind Direction: