Date: Monday, January 5, 2026 at 10:30 AM
Location: Myoko - Akakura Kanko - Upper Highlands main chutes
Coordinates: 36.89770883, 138.14448662
Elevation: 1360m (below treeline)
Aspect: E-NE
Activity: Snowpack assessment
Observers: Shane K, Nik N
The current snowpack structure and test results represent highly atypical conditions for the Myoko area. Historical snow depth data for Akakura Onsen shows the 2025-2026 season tracking notably below normal for early January, with approximately 150cm compared to the typical 200-300cm range by this date (with 320cm being the high mark in recent years).
The lower snowpack has resulted in the preservation of a reactive buried ice crust layer that would normally be more deeply buried and less consequential in Myoko’s typically deep, well-consolidated maritime snowpack. The CTH 1 propagation result with sudden planar failures are uncommon in this area. Users should be aware that the current snowpack behavior differs from normal patterns.
On the morning of Jan 5 at 10:30am, we conducted a snowpack assessment at 1360m on E-NE terrain following recent storm cycles. Column test results showed significant deterioration from December 28 assessment at similar location. Sudden planar failure on buried ice crust (65cm from ground, 85cm down from surface) with CTH 1 result. Total snow height 150cm. Avoided avalanche terrain due to concerning test results and poor visibility.
No avalanche activity observed. No signs of instability (whumpfing, cracking) noted during approach or fieldwork. However, poor visibility (S2-3 snowfall) limited ability to observe broader terrain features and potential avalanche activity on surrounding slopes. Avoided avalanche terrain for descent due to test results indicating potential instability on buried ice crust layer.
Spatial extent of this weak layer unknown - assessments on other aspects needed to determine if this is localized to E-NE exposures or more widespread. The weather-related formation (rain + sun crust) suggests it may be present across multiple aspects.
Total Snow Height: 150cm (variable 100-150cm depending on terrain features)
Structure: Buried ice crust (K hardness) at 65cm from ground (85cm down from surface) producing concerning test results. Recent storm snow: 30cm settled from January 2 storm, with additional 10cm from New Year’s Eve storm below that.
Hardness Profile:
Grain Types and Bonding:
Temperature Profile:
Stability Tests:
Comparison to December 28 Assessment (similar location):
Previous tests showed planar resistive break at CT Medium 9 on melt/freeze layer - fracture occurred but column remained stuck together. Current tests show significant degradation: failure now occurs on first hard tap with clean separation, indicating the interface has weakened over the past week despite storm loading above.
Layers identified:
Recent storm cycles delivered 40cm total new snow (settled measurements). No significant wind loading observed. Temperatures rose above zero on January 4 with solar radiation affecting snow surface quality.
Conditions during fieldwork:
Skiing quality marginal following above-zero temperatures and sun effect from January 4. Extensive sasa brush still exposed, limiting terrain options. Returned to resort infrastructure for descent due to combination of concerning stability test results, poor visibility, and brush hazards.
The buried ice crust at mid-pack depths is showing signs of weakening, with test results deteriorating significantly from resistant to sudden planar failure over a one-week period. The 40cm of storm snow has added load above this layer. The crust appears to be trapping moisture below, creating rounded grains with weaker bonding in the recent storm snow above. The temperature profile (-2°C to 0°C) shows the snowpack is near isothermal conditions at the crust depth, which may be contributing to the weakening interface.
While no instability signs were observed in the field, the propagation potential suggested by the CTH 1 result informed our decision to avoid avalanche terrain. The weather-related formation of this crust (combined rain and solar radiation) suggests it may be present across multiple aspects, though this has not been confirmed. Additional observations from other aspects and elevations are needed to understand the spatial extent of this weak layer.