Observation: NWAC Forecaster

All Observations

Basic Information

Observation Date:

December 12, 2021

Submitted:

December 12, 2021

Observer:

NWAC Forecaster - Andrew Kiefer

Zone or Region:

Mt Hood

Location:

Vista Ridge MHM (5400-6400ft, E-S-W aspects)

Recent Avalanches?

Yes

Cracking?

Isolated

Collapsing?

None Experienced

Sudden planar fracture with moderate force on a mid-storm interface buried 20cm. (SE aspect, 5800ft)

Storm snow since 12/8 has settled into an 80cm deep, right-side-up snowpack at this location. A mid-storm interface ↓20cm was reactive in snowpack tests (12/11 interface). It produced propagation in an extended column test (ECTP16) and sudden planar fractures with moderate force in shovel-tilt tests and hand shears.

Two small natural avalanches (D1) in wind drifted snow on the middle moraine in White River (E aspect near 5800ft).

The height of snow in undisturbed areas between 5200-6400ft averaged around 80cm. Still shallow coverage but fun skiing.

Minor cracking in wind drifted snow in the Vista Ridge area near Mt Hood Meadows (SE aspect, 6200ft)

Small cornices forming in the near treeline band on Vista Ridge (SE, 6200ft)

Advanced Information

Cloud Cover:

Obscured

Temperature:

20°F

Wind:

Moderate , SW

New/Recent Snowfall:

90-120cm (3-4ft) of new snow since 12/8

Obscured skies with short bursts of heavy snowfall (S1) in the AM. Moderate to strong winds blowing primarily SW. Brief periods of clearing skies and sunshine around 1300 when leaving the field.

Avalanche Observation Comments:

Two small natural avalanches (D1) in wind drifted snow on the middle moraine in White River (E aspect near 5800ft). Visibility was poor but the avalanches looked 12-24hrs old and 20-30cm deep.

In wind-sheltered areas between 5400-6400ft, storm snow since 12/8 has settled into an ∼80cm deep, right-side-up snowpack. A mid-storm interface ↓20cm was reactive in snowpack tests. It produced propagation in an extended column test (ECTP16) and sudden planar fractures with moderate force in shovel-tilt tests and hand shears. The snowpack is heavily wind affected above treeline with firm drifts on leeward slopes and many windward areas scoured to ground. Coverage is still shallow with plenty of grass, logs, rocks, and stumps poking through.

Problem	Location	Distribution	Sensitivity	Size	Comments
Wind 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	Layer Depth/Date: 20-40cm deep Comments: Uncertainty above treeline.

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