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Avalanche Forecast

Archived

Nov 29th, 2018–Nov 30th, 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. Check out the new forecaster BLOG which expresses these uncertainties.

Confidence

Low - Due to the number of field observations

Weather Forecast

The weather trend will start to stabilize as a high pressure system sets up, allowing dryer and cooler conditions. Clouds will linger through the weekend.FRIDAY: Mostly cloudy with scattered flurries/ alpine temperatures near -3/ generally light winds from the West/ freezing level 1200 mSATURDAY: Cloudy with snow up to 5 cm/ alpine temperatures near -4/ ridgetop winds light from the northeast/ freezing levels 1100 mSUNDAY: Cloudy with a trace of new snow/ alpine temperatures -8/ ridgetop winds light from the East/ freezing levels at valley bottom

Avalanche Summary

Several storm slabs were initiated by explosives up to size 1.5 on Thursday. Even though the avalanche hazard has decreased I suspect human triggered avalanches will be possible. If you're in the backcountry and have observations to share, please post to the Mountain Information Network.

Snowpack Summary

Up to 35 cm of recent storm snow fell earlier this week. Recent south and southwest winds have formed pockets of wind slab on leeward terrain. This adds an additional load onto a recently formed layer of feathery surface hoar. The distribution of this surface hoar layer is uncertain and at this time very isolated and difficult to validate. If you were to find it, 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. Little is known about this crust and how the snowpack above is bonding. I would investigate this bond before jumping onto large, planar terrain features. A mixed layer of melt-freeze crusts and sugary facets sits near the base of the snowpack. The snowpack is deepest in the alpine. 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". It mostly refers to adjacent regions in the Interior, but is a good read about our uncertainties in the current snowpack.

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.