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Avalanche Forecast

Archived

Jan 21st, 2025–Jan 22nd, 2025

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Glacier.

Small wind slabs are forming at the surface but our main concern remains the persistent weak layer down 30-60cm.

Excellent skiing can be found in locations sheltered from the wind.

Confidence

Moderate

Avalanche Summary

Explosives testing on round hill ridge on Tuesday produced Size 1.5 Wind slabs averaging 10cm deep.

A persistent slab avalanche was reported by a third party in the Kors-Thomas bowl of Avalanche Mountain on Sunday. No details of the event are available but it appears to have been skier triggered.

Snowpack Summary

Periods of moderate wind creating fresh wind slab at the surface. Sheltered areas have ~15cm of cold, faceted snow sits atop a denser, wind-pressed layer. Below this lies a weak interface (Jan 7th layer) down 30-60cm, comprised of surface hoar (all aspects) and or a thin crust on steep S aspects.

In the start zone of Mt Fidelity, moderate "resistant" & "sudden planar" snowpack test results were found on the Jan 7 layer.

Weather Summary

Tonight Clear periods. No precipitation. Ridge wind NW 20-30 km/h. Freezing level (FZL) at valley bottom.

Wednesday A mix of sun & cloud. No precipitation. Alpine high -8. Ridge wind W 15-25. FZL 600m.

Thursday Mainly cloudy with isolated flurries. Trace precipitation. Alpine high -8. Ridge wind W 20 gusting to 45. FZL 700m.

Friday A mix of sun & cloud. No precipitation. Alpine high -11. Light ridge wind gusting to 35

Thursday

Terrain and Travel Advice

  • Be especially cautious as you transition into wind-affected terrain.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks, or recent avalanches.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.