Avalanche Forecast
Regions: Cascades - North East.
Dangerous avalanche conditions are lingering after a major winter storm stressed older weak layers in the snow. Use caution near slopes 35 degrees and steeper and avoid lingering below steep terrain. Put a large buffer of space between where you travel and any slopes that are steep enough to slide.
Discussion
Washington Pass picked up over 3 feet of snow and 3.2" of water equivalent between Thursday afternoon and Saturday. Observers reported large natural avalanches in Silver Star creek, the Delancy Ridge area, on a northwest aspect of Silver Star Mountain, and a northeast aspect of Hinkhouse peak. Observers witnessed an avalanche run on Saturday around noon on a north aspect of Peak 6460ft near Silver Star creek. On Sunday, an observer near Vasiliki Ridge reported collapses that covered areas as wide as 30 feet.
Snowpack Discussion
New Regional Synopsis coming soon. We update the Regional Synopsis every Thursday at 6 pm.
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Avalanche Problems
Persistent Slabs
You can trigger dangerous and surprising avalanches even from below or on adjacent slopes. Any triggered avalanche could be big enough to kill you and could break widely across the terrain. Use caution on or near slopes 35 degrees and steeper. Put a large buffer of space between you and any avalanche terrain. Watch out for rocky terrain, steep convexities, and unsupported slopes where you could trigger avalanches more easily.
Be observant by looking and listening for signs of avalanche danger. Recent avalanches, whumpfing collapses, and cracks shooting through the snow are signs that you could trigger a persistent slab avalanche. Take time to dig in the snow and look for older, weak layers. You can find a layer of facets that formed in November, often under a thin crust about 2.5-3 feet below the snow surface. You can use snowpack tests to help identify this layer.
Release of a cohesive layer of soft to hard 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 Slabs.
The best ways to manage the risk from Persistent Slabs is to make conservative terrain choices. They can be triggered by light loads and weeks after the last storm. The slabs often propagate in surprising and unpredictable ways. This makes this problem difficult to predict and manage and requires a wide safety buffer to handle the uncertainty.
This Persistent Slab was triggered remotely, failed on a layer of faceted snow in the middle of the snowpack, and crossed several terrain features.
Persistent slabs can be triggered by light loads and weeks after the last storm. You can trigger them remotely and they often propagate across and beyond terrain features that would otherwise confine wind and storm slabs. Give yourself a wide safety buffer to handle the uncertainty.
Aspects: North, North East, East, West, North West.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 2