Avalanche Forecast
Issued: Feb 26th, 2019 4:12PM
The alpine rating is Wind Slabs and Persistent Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeFresh wind slabs are sitting on top of buried wind slabs that are sitting on facets (weak, sugary snow). The fresh wind slabs are touchy and the buried wind slabs may remain reactive to human triggers longer than is typical for this region.
Summary
Confidence
High - The weather pattern is stable
Weather Forecast
TUESDAY NIGHT: Clear / Light to moderate, northeasterly winds / Alpine low -16.WEDNESDAY: Sunny / Light, northeasterly winds / Alpine high -8.THURSDAY: Mostly sunny / Light, northerly winds / Alpine high -8.FRIDAY: Sunny / Light, northwesterly winds / Alpine high -16.
Avalanche Summary
On Monday, several natural wind slab avalanches up to size 1.5 were reported on a variety of aspects in the alpine. Over the past week there have been numerous 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. These layers have created a low likelihood, high consequence scenario that requires discipline and careful terrain selection to manage effectively.
Snowpack Summary
Strong northeasterly ridge-top winds on Monday created fresh wind slabs on lee features at treeline and above. Additionally, there are buried wind slabs on a variety of aspects that are sitting on facets (sugary snow) which may cause them to remain reactive to human triggers longer than what is typical for a wind slab problem in this region.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 treeline elevations.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
Wind Slabs
Fresh wind slabs are sitting on top of buried wind slabs that are sitting on facets (weak, sugary snow). The fresh wind slabs are touchy and the buried wind slabs 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, Treeline.
Likelihood
Expected Size
Persistent Slabs
There are two persistent weak layers in the snowpack, buried approximately 40 cm and 75 cm below the surface. These layers have created a low likelihood, high consequence scenario.
Avoid low elevation cut-blocks where this layer is well preserved.Use conservative route selection, choose moderate angled terrain with low consequence.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
Valid until: Feb 27th, 2019 2:00PM