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Propagating extended column tests and recent avalanche

Location Name: 
Gray Butte
Region: 
Mt. Shasta
Date and time of avalanche (best estimate if unknown): 
Wed, 03/06/2019 - 3:45am
Observation made by: 
Forecaster
Red Flags: 
Recent avalanche activityWhumphing noises, shooting cracks, or collapsingRecent loading by new snow, wind, or rain

Location Map

96067 Mount Shasta , CA
United States
41° 20' 54.2868" N, 122° 11' 34.0836" W
California US

Avalanche Observations

Details

March 6, 2019 - Gray Butte

Today started off with heavy at times rain and snow. Snow levels fluctuated around 6,000 feet. In the afternoon, precipitation continued, although showery in nature. A few very brief sections of blue sky occurred, but were very short lived. Temperatures were in the mid-twenties, but the air felt warmer and like a "greenhouse" effect. Trees began to off-load heavy snow.

The bottom line out there today was an upside down snowpack. Above 7,000 feet, new snow, 12-15 inches deep sits on top of a widespread, thick crust layer. New snow is moist on top with dryer snow below. Fully propagating extended column tests were easily produced on all southerly and easterly aspects, near and above treeline.  Whoomfing and shooting cracks were observed on the skin up and along ridgelines. On top of Gray Butte, an intentional cornice drop onto an easterly slope (8,000 feet) produced the avalanche in the featured image. This D2 storm slab was about 150 feet wide and ran to the bottom of the slope through sparse trees. 

Characteristics

Avalanche Type: 
Slab
Trigger type: 
Other - explain below
Slope: 
38degrees
Aspect: 
East
Elevation: 
8 000ft.
Terrain: 
Near Treeline
Weak Layer: 
Storm Snow
Bed Surface: 
Storm Snow
Crown Height: 
1 ft
Avalanche Width: 
150ft.
Avalanche Length: 
400ft.
Number of people caught: 
0
Number of partial burials: 
0
Number of full burials: 
0

Weather Observations

Details

Sky: Obscured, foggy

Precip: less than 1in/hour during tour, but prior snow amounts up to 15 inches in last 24 hours, heavy/wet

Wind: south to west, moderate, gusty. Most new snow too heavy for wind transport

Statistics

Cloud Cover: 
100% of the sky covered by clouds
Precipitation: 
Snow
Accumulation rate: 
Less than 1 in. per hour
Air temperature: 
Below Freezing
Air temperature trend: 
Cooling
Wind Speed: 
Moderate
Wind Direction: 
West