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Avalanche Forecast

Archived

Dec 3rd, 2019–Dec 4th, 2019

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
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.

Regions

Glacier.

A natural avalanche cycle will peak this afternoon as strong winds trigger storm slabs!

Weather Forecast

Today: 15-20cm of new snow, winds will be light to moderate possibly gusting strong this afternoon out of the South, and the freezing level should stay below valley bottom (VB). Tonight: Another 10cm, winds increasing from the SW, and temps staying cool with the FL staying well below VB. Flurries for Wednesday, and a clearing trend on Thursday

                                                                                                                                                                                                                                     

Snowpack Summary

30 of new snow covers a facetted upper snowpack and previously wind affected surfaces. The two main interfaces to watch for are the storm slab interface down 30cm+ and the Nov 23rd surface hoar/ crust buried 40-60cm. Multiple buried crusts exist lower in the snowpack, but recent profiles are showing no significant shears on stability tests.

Avalanche Summary

We should see a natural avalanche cycle today with the 20cm of new snow that fell last night, plus another 15cm forecasted today! No new avalanches were reported from the highway or the backcountry yesterday; however, we are already starting to see some activity in the Highway corridor this morning!

Confidence

Problems

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

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.