Observation: NWAC Forecaster

All Observations

Basic Information

Observation Date:

December 9, 2021

Submitted:

December 9, 2021

Observer:

NWAC Forecaster - Andrew Kiefer

Zone or Region:

Mt Hood

Location:

Little Zigzag Canyon (5800-6400ft, E-S-W aspects)

Recent Avalanches?

Yes

Cracking?

Isolated

Collapsing?

None Experienced

A shooting crack in wind drifted snow in Sand Canyon on Mt Hood (E aspect, 6200ft).

A small skier triggered avalanche (D1) in wind drifted snow that broke 3-6in deep and 15ft wide in Sand Canyon on Mt Hood (E aspect, 6200ft)

Snow depths are highly variable. In this gully feature on the southside of Mt Hood 1-2ft of snow exists on the wind-loaded east-facing slope, while the west-facing slope is scoured to bare ground.

New snow beginning 12/8 fell on bare ground up to 7000ft on Mt Hood. Plenty of rocks and vegetation still poking through here at 6000ft on a southerly aspect around 11am on 12/9.

Advanced Information

Cloud Cover:

Obscured

Temperature:

15-20°F

Wind:

Strong , W

New/Recent Snowfall:

12in of new snow since 12/8 (as of noon on 12/9)

Snowfall rates increased to 1in per hour late morning with strong and gusty westerly winds. Poor visibility with whiteout conditions above treeline.

Avalanche Observation Comments:

Triggered two small, shallow avalanches (D1) that broke 3-6in deep and 10-15ft wide in wind drifted snow on east facing slopes near 6200ft.

A winter snowpack is rebuilding and conditions are changing rapidly. So far, 12in of new snow since 12/8 was redistributed by strong and gusty westerly winds. The height of snow was highly variable throughout the terrain from bare patches to 2ft+ thick drifts. New snow since 12/8 fell on mostly bare ground below 7000ft, and consolidated but thin snow cover above. Snow depths below treeline were still below threshold for avalanches mid-day 12/9.

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: 6-12in and thickening

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