Avalanche Forecast
Issued: Feb 24th, 2019 4:20PM
The alpine rating is Persistent Slabs and Wind Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeA persistent weak layer that has been most pronounced at lower elevations has created a low likelihood, high consequence scenario that requires discipline and careful terrain selection to manage effectively.
Summary
Confidence
High - The weather pattern is stable
Weather Forecast
SUNDAY NIGHT: Clear / light, northeasterly winds / Alpine low -19.MONDAY: Sunny / light, northeasterly winds / Alpine high -15.TUESDAY: Sunny / light, northeasterly winds / Alpine high -14.WEDNESDAY: Sunny / light to moderate, easterly winds / Alpine high -9.
Avalanche Summary
Over the past week there have been near daily reports of persistent slab avalanches, some of which were human triggered. They have been large avalanches (size 2-2.5), occurring on a variety of aspects at treeline and below treeline elevations. They are likely failing on the persistent weak layer of surface hoar and/or crusts that were buried mid January.
Snowpack Summary
5-10 cm of recent snow has been redistributed by moderate to strong southwest winds. This snow sits on 10-25 cm of low density snow or older wind slabs that formed on a variety of aspects in many areas. There are two prominent weak layers in the upper snowpack. One was buried at the end of January, and the other was buried mid January. They are approximately 40 and 75 cm below the surface. Both layers consist of a mixture of surface hoar (weak, feathery crystals) and facets (sugary snow), which likely also sit on a sun crust on steep, south facing slopes. These weak layers are most prominent at treeline and below.Very sporadically, failures have occurred near the base of the snowpack in this region, or in neighboring regions. These avalanches have primarily been in steep, rocky, high alpine areas with a shallow snowpack.
Problems
Persistent Slabs
There are two persistent weak layers in the snowpack, buried approximately 40 cm and 75 cm below the surface. Avalanches continue to be triggered on either of these layers.
Any steep opening in the trees should be treated as suspect.Be aware of the potential for wide propagations.Avoid convexities as well as steep, open and/or sparsely treed slopes at and below treeline.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Wind Slabs
Buried wind slabs that are sitting on facets (weak, sugary snow) in rocky alpine terrain may remain reactive to human triggers longer than is typical for this region.
Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Avoid slopes that sound hollow or drum-like.Steep and rocky terrain are likely places to trigger buried wind slabs.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Feb 25th, 2019 2:00PM