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Avalanche Forecast

Archived

Feb 28th, 2022–Mar 1st, 2022

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

Regions

Northwest Inland.

Reactive wind slabs continue to form in upper treeline and high alpine leeward features. Continue to investigate the crust that was buried on February 9th as it now has a 50-70cm thick slab above it that could produce larger avalanches. 

Confidence

Moderate -

Weather Forecast

Monday night: Mostly cloudy. 5cm of new snow overnight. Winds moderate from the southwest to southeast. -5°C.

Tuesday: Mostly cloudy. 5cm of new snow. Winds moderate from the south. -5°C.

Wednesday: A mix of sun and cloud. No precipitation. Winds light and variable. A low of -4°C and a high of 0°C.

Thursday: A ridge starts to build bringing a mix of sun and cloud. No precipitation. Winds light and variable. A low of -5°C and a high of 1°C. 

Avalanche Summary

No new avalanches were reported over the weekend. 

Snowpack Summary

Monday and Tuesday will bring 10-15cm of snow which will get blown into small wind slabs in upper treeline and alpine leeward features. Wind slabs continue to form on a variety of surfaces including wind effected slopes, facets, or weak feathery surface hoar crystals in sheltered areas. 

The upper snowpack appears to be bonding to a rain crust now buried 50-70cm. However, the field team did observe reactivity in test profiles on this layer (ECTP29) and the recipe for avalanches exists at this interface.

The lower snowpack is effectively capped, making human triggering of avalanches on deeper weak layers unlikely.

Terrain and Travel

  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Highmark or enter your line well below ridge crests to avoid wind loaded pillows.
  • Use caution above cliffs and terrain traps where even small avalanches may have severe consequences.
  • Keep in mind the crust offers an excellent bed surface for avalanches.

Problems

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.

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.