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Avalanche Forecast

Archived

Feb 28th, 2020–Feb 29th, 2020

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

Regions

Glacier.

The snow load over the February 22nd surface hoar is increasing and priming for a trigger

Weather Forecast

5cm today, wind light south. Freezing levels could rise to 2000m before dropping this afternoon with a period of intense precip. Tonight 10cm with falling temperatures and winds picking up to strong from the west. Periods of convective snowfall through the day tomorrow, freezing level falling to 1000m and winds dropping off to light, west.

Snowpack Summary

A widespread 3-7mm surface hoar layer on all aspects in combination with a 2-4cm sun crust was buried on February 22nd and now has up to 50cm of storm snow above it. This layer has been observed to 2450m. No other layers are currently active in the 3.5m snowpack of mostly rounded grains.

Avalanche Summary

A field team ski cut predictable small convexities yesterday with isolated results to sz 1 on the Feb 22nd surface hoar. Numerous reports of skier-triggered avalanches on the February 22nd layer to sz 1.5 this week. More snow and rising temperatures today will likely overload this weak layer causing natural avalanches on all aspects.

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Friday

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.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.