MYOKO SNOWPACK OBSERVATIONS REPORT

Date: Wednesday, March 11, 2026 at 1:16 PM
Location: Myoko - Akakura-san - TL N/NE slope
Coordinates: 36.88132, 138.13000
Elevation: 1821m (5976 ft)
Aspect: N/NE (heading 031)
Activity: Pit for snow report
Observers: Nik N, Ciaran H

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Concerning results observed: Reactive failures were observed in CT at/above a 26-38cm rain-freeze crust with faceted 1mm snow beneath interface

No avalanche activity, cracking, or whumpfing was observed during fieldwork. However, compression testing produced two failures in the upper pack: first at 30cm (planar) and second near 38cm associated with the rain-freeze crust. Observer reported the crust interface as highly reactive in testing, with a block that did not fully eject but slid out with light additional force.

QUICK SUMMARY - HS 230cm, 140cm pit at TL, storm snow over 26-38cm crust, CTH25 at 30cm and CTH30 near 38cm

At 1:16 PM on March 11, a snowpack pit was completed at Akakura-san treeline on N/NE terrain (1821m). HS measured 230cm with pit depth 140cm. Upper snowpack contained recent storm snow over a rain-freeze crust from 26-38cm. CT produced two failures in the hard tap series: CTH25 at 30cm (planar) and CTH30 near 38cm on the crust interface.

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AVALANCHE SUMMARY - NO ACTIVITY OBSERVED; observations limited to treeline travel and a single pit location

No avalanche activity was observed. No direct instability signs (cracking, whumpfing) were reported. Spatial confidence is limited because observations were centered on treeline terrain and one pit site.

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SNOWPACK SUMMARY - Storm snow over rain-freeze crust (26-38cm) with facet development below; CT reactivity at CTH25/30cm and CTH30/~38cm

Total Snow Height (HS): 230cm
Pit Depth: 140cm

Hardness Profile (surface down):

• 0-14cm: F
• 14-25cm: 4F
• 25-31cm: 2F
• 31-37cm: 1F
• 38-40cm: P
• 40-55cm: 1F
• 56-63cm: 2F
• 63-77cm: 1F
• 77-120cm: P
• 120-140cm: K

Grain Types and Bonding:

• 0-26cm: recent storm snow
• 26-38cm: rain-freeze crust (observer notation: MfCL)
• ~39-85cm: previous seasonal snow
• 85-90cm: dust-discolored layer
• 90-140cm: consistent seasonal snow
• Interface above/below rain-freeze crust showed faceting; sugary faceted grains (about 1mm) were observed below the interface

Stability Test:

• CTH25 (RP): 30cm, resistant planar fracture; block did not fully eject but slid out with light additional force
• CTH30: ~38cm on crust interface; observer reported high reactivity

Temperature Profile (deg C, every 10cm from surface):

• 0cm: 0.1
• 10cm: -2.5
• 20cm: -3.7
• 30cm: -3.2
• 40cm: -2.6
• 50cm: -2.1
• 60cm: -1.5
• 70cm: -1.1
• 80cm: -0.8
• 90cm: -0.4
• 100cm: -0.2
• 110cm: -0.1
• 120cm: 0.0
• 130cm: 0.0
• 140cm: -0.1

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WEATHER SUMMARY - Scattered clouds, no wind, -4C air temp; prior 24-hour storm cycle with light wind and storm snow

Conditions during fieldwork:

• Sky: Scattered clouds
• Precipitation: Not recorded during observation
• Air temperature: -4C
• Wind: No wind observed
• Surface snow temperature: 0.1C

Recent weather:

• 24-hour storm cycle prior to observation
• Storm snow with light wind

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TRAVEL CONDITIONS - Crust-affected and heavy riding quality on descent

Travel and ski quality were reported as crust-affected and heavy on the ride down. No additional terrain-trap notes were submitted.

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ASSESSMENT - Single-site treeline pit indicates reactive upper-pack structure at/above crust despite no obvious surface red flags

This observation shows a storm-snow-over-crust setup with test reactivity at 30cm and near 38cm, plus faceting below the crust interface. No avalanche activity or obvious instability signs were observed, but the CT results indicate a weakness that can still fail under loading at this site. Because this is a single treeline pit, spatial extent of that reactivity across aspect and elevation remains uncertain.

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