Cold weather continues! Please submit your observations to the MIN.
Confidence
Moderate - Wind effect is extremely variable
Weather Forecast
Cold and clear overnight with moderate northeast winds. Cold and clear on Wednesday with valley temperatures around -20, some chance of thin high cloud moving in from the northeast. High cloud on Thursday with light westerly winds and no precipitation. Mostly clear with moderate southwest winds and a trace of new snow on Friday.
Avalanche Summary
No new reports of avalanches. Wind slabs may be triggered on all aspects due to the changing wind directions associated with recent storms. Shallow snowpack areas continue to be a concern for weak facetted (sugary) crystals that may fail to support the more recent storm snow. These weak areas are not expected to improve during this period of cold weather.
Snowpack Summary
The recent storm snow has been transported by northeast winds into wind slabs on south and west aspects. In some areas these wind slabs may sitting on an old scoured surface that was stripped by previous strong westerly winds that developed wind slabs on north and east aspects. The newer wind slabs are probably easier to trigger, but the old wind slabs may continue to release with the added load of a rider, especially where they are sitting on a shallow weak sugary base. Travel conditions have been challenging and little change is expected until the next warm up helps to settle the snowpack.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of 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 Slab.