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Avalanche Forecast

Archived

Dec 1st, 2018–Dec 2nd, 2018

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

Regions

Lizard-Flathead.

With few field observations, uncertainty exists around the buried weak layers in the snowpack. Natural avalanche hazard has tapered off but human triggers are still possible, especially where the slab sits above a weak layer. Forecaster BLOG here.

Confidence

Moderate - The weather pattern is stable

Weather Forecast

As the upper ridge sets up we will move into a period of cooling, drying and fairly light, northerly winds. SUNDAY: Mix of sun and cloud/ alpine temperatures near -5/ generally light winds from the northeast/ freezing level 1100 mMONDAY: Cloudy/ alpine temperatures near -10/ ridgetop winds light from the northeast/ freezing levels valley bottomTUESDAY: Mix of sun and cloud/ alpine temperatures -12/ ridgetop winds light from the southwest/ freezing levels valley bottom.

Avalanche Summary

Several small human triggered storm slabs up to size 1 were reported on Saturday. Even though the avalanche hazard has decreased I suspect human triggered avalanches will be possible, especially where the storm slab sits above a weak layer like surface hoar or the early November crust. If you're in the backcountry and have observations to share, please post to the Mountain Information Network.

Snowpack Summary

Another 7 cm of snow overnight adding to the 55 cm of recent storm snow that fell earlier this week. Recent south and southwest winds have formed pockets of wind slab on leeward terrain, however the winds have switched to a northerly direction and are potentially redistributing the new snow on opposite. slopes. Below the surface exists a series of crusts and a feathery surface hoar layer. We have a lot of uncertainty around this weak layer, its distribution is spotty. I suspect it could exist on sheltered slopes in the alpine and at treeline. Deeper in the snowpack a melt-freeze crust exists at treeline and into the alpine on all aspects. Reports indicate that the slab above this crust may be more reactive on northeasterly aspects. I would investigate this bond before jumping onto large, planar terrain features. At the bottom of the snowpack you'll likely find melt-freeze crusts and sugary weak facet crystals. At treeline the average snowpack depths are 80 cm. These depths taper rapidly at lower elevations.Check out the new forecaster blog post "The Buzz". Discussing uncertainty with what lies beneath...

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.