Increasing avalanche hazard today with the incoming storm. Give overhead avalanche paths a wide berth, especially during periods of heavy snowfall.
Weather Forecast
A winter storm is forecasted to arrive in the area later this morning, bringing anywhere between 10-30cm of snow, with moderate to strong W winds and freezing levels rising to 1400m.
Snowpack Summary
35cm of recent snow is settling. Mid to lower snow pack is rounding out and becoming more settled. The Dec. 8 surface hoar/facet layer, down ~90cm, is mostly unreactive in snowpack tests around Rogers Pass. The Nov. 28 surface hoar layer, down ~125cm, is still well preserved in certain areas and is giving hard sudden planar results.
Avalanche Summary
No new avalanches were observed in the highway corridor yesterday. Ski operations adjacent to Glacier National park observed a few slab avalanches within the storm snow, less than 30cm in thickness. As the new storm system rolls in, expect natural activity to pick up.
Confidence
Timing, track, or intensity of incoming weather system is uncertain
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.
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.