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Avalanche Forecast

Archived

Dec 23rd, 2019–Dec 24th, 2019

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

Regions

Glacier.

The natural cycle may have tapered off, but human triggering remains likely in areas that have not seen avalanche activity since the weekend.

Minimize your exposure to overhead hazard today!

Weather Forecast

A benign weather pattern with cooling temperatures and mixed skies is the trend for this week in Rogers Pass.

A mix of sun and cloud today. Freezing levels are forecast at 900m with an alpine high of -8°C.

Snowpack Summary

The Atmospheric River dumped 75mm of precipitation over the weekend, and is settling slowly with cooling temperatures. The Dec 11th SH (5-12mm) is now down 90-120cm, and sits on a rounding midpack. The Nov 23 SH/Cr is down 160-185cm. Early season crusts still persist in the lower snowpack.

Avalanche Summary

The natural avalanche cycle has tapered off, however human triggered avalanches in areas that haven't slid remain likely. This weekend's storm saw numerous natural and artillery triggered avalanches to size 3.5 on all aspects and elevations. Slides released in the storm snow then stepped down to the persistent slab (Dec 11 SH), down 90 - 120cm.

Confidence

Due to the number of field observations

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.

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.