Southerly sluffs and northerly propagations

Location Name: Forecaster Observation: Southern Whitefish Range Observation date: Tuesday, February 25, 2020 - 14:00	Is this an Avalanche Observation: No

Observation made by: Forecaster

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Quick Observation

Spent the day around Whitefish Mountain Resort.

Observed small debris piles from loose dry avalanches on southerly aspects at mid-elevations. Details in avalanche tab.
Cracking in new snow at upper elevations on northerly aspects.
Found surface hoar buried beneath 30 to 40 cms (~10 to 15 inches) of new snow in areas that were sheltered from the wind and sun prior to storm snow.
Numerous extended column tests produced propagating results with easy force. All tests failed on surface hoar.

Travel Details

Region:

Whitefish Range - Southern (south of Coal Creek)

Route Description:

Activity:

Skiing

Snowpack Details

Snowpack and Weather Details:

Terrain

Elevation of observation:

Above 6500 ft

Aspect(s) of observation:

Red Flags:

Shooting cracks

Persistent Weak Layers:

Surface Hoar

Buried

More comments about the snowpack and weather:

Sky cover went from obscured to broken throughout the day. S-1 throughout the morning and early afternoon hours. Numerous pits dug on north aspect at upper elevation. Test results were dependent on the distribution of surface hoar. ECTP2 down 35 cms. Similar test results in nearby locations.

Wind Speed:

Calm (No air motion)

Air temperature:

Below Freezing

Sky Cover:

Mostly Cloudy (BRK)

Highest Precipitation Rate:

Very Light Snowfall (S-1)

Avalanche Details

Avalanche Details:

Date and Time of Avalanche:

Tuesday, February 25, 2020 - 01:00

Number of avalanches:

Avalanche Type:

Loose Dry/ Sluff

Failure Plane/Weak Layer:

Within storm snow

More information or comments about the avalanche:

Observed from a long distance away and the timing of the event is speculated. Appeared there were two, maybe three loose dry avalanches in skook chutes and then one observed in Halfmoon. Uncertain if the loose dry in Halfmoon was skier triggered or natural (noted ski tracks adjacent to avalanche).

Trigger

Trigger:

natural

Terrain

Start Zone Slope Angle:

Aspect:

Southwest

Starting Elevation:

near-treeline

Size

Destructive Size:

D1 Relatively harmless to people.

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