Observation: NWAC Observer

All Observations

Basic Information

Observation Date:

March 24, 2023

Submitted:

March 24, 2023

Observer:

NWAC Observer - Keeley Rideout

Zone or Region:

West South

Location:

Bullion Basin (4000-6500ft, All Aspects)

Recent Avalanches?

None Observed

Cracking?

None Experienced

Collapsing?

None Experienced

SW aspect, refrozen sizeable rollerballs from warm weather/ wet loose activity earlier this week.

Pit @6000ft, NE Aspect, 38 degree slope.

Failure ~21cm down at ECTN2. It failed just beneath the crust in the uppermost old snow.

The diagonal blue-ish layer is the 3cm thick ice crust ~95cm down. Notice how cohesive that column is!

Advanced Information

Cloud Cover:

Mostly Cloudy

Temperature:

28°F

Wind:

Calm , W

New/Recent Snowfall:

HN24: 20cm

Broken clouds with intermittent light snowfall from 9am - 3pm. We saw blowing snow and spindrift near ridgelines, though winds were calm all the way to 6000ft at all aspects. The new snow is low density and easily to transport.

Avalanche Observation Comments:

Lots of evidence of wet loose activity, especially on south aspects, from the warm weather before this storm rolled in. Some mild, skier-triggered sloughing of new snow on steep slopes.

We first skied a SW slope and had to navigate beach ball to bowling ball sized refrozen chunks of debris from leftover wet loose activity earlier in the week. Areas that were clear of debris had ~10cm of new snow atop a bulletproof crust.

We then dug a pit on a NE aspect at 6000ft. Total snow depth was 270cm. Our pit depth was 155cm. We found new snow depth was ~20cm which sat atop a thin crust on the old snow interface. The old snow got denser 50cm from snow surface, and an old 3cm thick crust 95cm down was well-bonded with snowpack above and below.

An ECT failed at ECTN2 @21cm below the thin old snow crust. The failure did not propagate. Upon skiing slopes around 38 degrees we started some short running sloughs of the new low density snow. We experienced this on the SW slope as well.

Problem	Location	Distribution	Sensitivity	Size
Wind Slab	N E S W	Isolated Specific Widespread	Unknown	D1 D1.5 D2 D2.5 D3 D3.5 D4 D4.5 D5
Dry Loose	N E S W	Isolated Specific Widespread	Unreactive Stubborn Reactive Touchy	D1 D1.5 D2 D2.5 D3 D3.5 D4 D4.5 D5
Storm Slab	N E S W	Isolated Specific Widespread	Unreactive Stubborn Reactive Touchy	D1 D1.5 D2 D2.5 D3 D3.5 D4 D4.5 D5

Though the storm snow resulted in sloughing/dry loose activity elsewhere in the area the new snow may behave like storm slab.

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