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Large Natural Avalanche in Avalanche Gulch

Location Name: 
Avalanche Gulch
Region: 
Mt. Shasta
Date and time of avalanche (best estimate if unknown): 
Sun, 04/07/2019 - 11:00pm
Observation made by: 
Forecaster
Red Flags: 
Recent loading by new snow, wind, or rainRapid warmingObvious avalanche path

Location Map

United States
41° 22' 40.8648" N, 122° 12' 47.8656" W
US

Avalanche Observations

Details

A large (R3/D3.5) natural loose-wet avalanche occurred in Avalanche Gulch between Saturday, April 6th and Monday, April 8th. This loose-wet avalanche likely released during a period of rapid warming and heavy precipitation. Best estimate puts this avalanche on Sunday, April 7th at 11 p.m.

This avalanche left an impressive track and debris pile. The debris pile was 5-8 feet deep with spots up to 15 feet deep. the track was 20 to 50 feet wide and nearly a mile long. Low visibility limited observations of the crown. 

Avalanche Classification Code: WS-NS-R3-D3.5-U

Path Description

  • Estimated elevation range of run out zone: 8,200 - 7,500 feet
  • Estimated elevation range of track: 10,000 - 8,200 feet
  • Estimated elevation range start zone: 11,000 - 10,000 feet
  • Estimated Vertical fall (top of start zone to lower runout zone): 3,500 feet
  • Length of path run: 2 mile

Path Characteristics

  • Exposure to wind/drifting snow: Leeward in northerly wind
  • Exposure to solar: Shaded in the morning, afternoon sun
  • Surface roughness: Scattered small cliffs and rocks
  • General terrain shape: Large concave feature
  • Estimated frequency: Infrequent
  • Destructive Potential: D3.5 = could destroy a large truck, small building, or break some large trees. 

  • Large pile of Avalanche debris


  • Above Treeline Track 


  • Sympathetic Crown 


  • Terminus of Avalanche 

 
 

Characteristics

Avalanche Type: 
Wet
Trigger type: 
Natural
Slope: 
38degrees
Aspect: 
South
Elevation: 
9 100ft.
Terrain: 
Above Treeline
Weak Layer: 
Unknown
Bed Surface: 
Unknown
Avalanche Width: 
100ft.
Avalanche Length: 
1 600ft.

Weather Observations

Details

The recent storm to impact the Mount Shasta area has been warm, wet and rainy. Since it began early Saturday morning (04.06.2019) 3.83 inches of water has fallen as rain at 7,600 feet on Mount Shasta.  Above freezing temperatures have been recorded since noon on Saturday. An average temperature of 34 degrees F since midday on Saturday. This rain on snow has settled the snow nearly 10 inches over the last three days. 

Statistics

Cloud Cover: 
75% of the sky covered by clouds
Blowing Snow: 
Yes
Precipitation: 
Snow
Accumulation rate: 
Less than 1 in. per hour
Air temperature: 
Below Freezing
Air temperature trend: 
Warming
Wind Speed: 
Moderate
Wind Direction: 
West