Observation: NWAC Observer

All Observations

Basic Information

Observation Date:

March 10, 2023

Submitted:

March 10, 2023

Observer:

NWAC Observer - Drew Lovell

Zone or Region:

East North

Location:

Harts Pass Area (All aspects, 5000'-7300')

Recent Avalanches?

Yes

Cracking?

Isolated

Collapsing?

None Experienced

Test pit targeting the Feb.12 MFcr, down 90-120cm throughout the zone. Weak grains were found below the crust, but the interface does not present a stability concern at this time.

A passing skier is lost in a cloud of low-density powder, illustrating the lack of cohesion in recent snow surfaces.

Small, non-destructive Dry Loose sluffs were both running naturally and easily pushed by skiers over recent days.

Advanced Information

Cloud Cover:

Overcast

Temperature:

14°F

Wind:

Moderate , SE

New/Recent Snowfall:

20cm storm snow since Mar.7

Moderate SE winds at ridge crests on Mar.9 found ample low-density snow available for transport.

Avalanche Observation Comments:

Cracking within recent wind-deposited snow along ridge crests on Mar.9 prompted us to avoid steep, alpine starting zones. We suspect that we may have been able to trigger sz.1-1.5 Wind Slabs, which are likely becoming stubborn as of Mar.10.
Small (sz.1) Dry Loose avalanches were widespread and touchy, and warranted some attention by skiers in steep terrain.

Snow depths throughout the zone range from about 220-330cm.
Recent storm snow accumulations since late Feb. total ~120-130cm locally. This contributes to a right-side up upper snowpack that trends from low-density (F-hardness) to 1F+ hard snow with a good bond over the Feb.12MFcr, down 90-120cm. A thin layer of rounding facets exists below the crust, but does not seem to present a stabiity concern at this time.
Older Wind Slabs (down 50-70cm) may produce Hard, Resistant results in small column tests but are now unreactive to skiers.
A mixed bag of low-density stellars and surface hoar was buried in the zone on Mar.7, by 10-20cm low density storm snow. This seemed to contribute to the fast and pushy nature of skier-triggered Dry Loose sluffs. We suspect that some recently developed Wind Slabs from mod. SE winds on Mar.9 may overlie these previous weak surfaces.
Weak sun crusts were similarly buried on Mar.7 on solar slopes.

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: Mar.9 20-30cm Comments: Cracking observed at ridge crests during wind event on Mar.9
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	Layer Depth/Date: 10-20cm Comments: Weak sun crusts buried Mar.7 may limit Dry Loose activity on solar slopes

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