Wind slabs and persistent weak layers will be slow to heal due to the continued cold weather.
Weather Forecast
Some thin high cloud overnight with moderate easterly winds. Expect lows around -25. Clear and cold on Tuesday with light northerly winds and alpine highs around -18. Mostly clear on Wednesday with moderate-strong northerly winds. Cloud developing on Thursday with moderate westerly winds and a trace of snow.
Avalanche Summary
No new reports of avalanche activity. The bigger problem is the lingering deeper weakness: last week an avalanche near Corbin on a wind affected, cross-loaded slope was triggered where a fresh windslab was above weak facets. Evidence of a natural size 2.5 persistent slab avalanche was also noted on a treeline feature in the same drainage. While technically this area is in the Lizard/Flathead region, these avalanches illustrate conditions in the South Rockies. Where you get a combination of weak sugary snow lower in the snowpack and a supportive upper slab, conditions are ripe for avalanches to be human-triggered.
Snowpack Summary
Up to 20cm of new arrived Saturday night and Sunday. Moderate to strong NE winds drifted the snow into soft slabs. In general, there is very little structure to the snowpack, with low-density snow sitting over soft sugary facets. Travel is very challenging as a result. A variable interface that formed during the cold snap in early December can be found buried 30-50 cm deep. This interface consists of weak faceted (sugary) snow and preserved surface hoar in sheltered areas. The interface is likely most reactive in wind-affected terrain where it is covered by a more cohesive wind slab. Hazards such as stumps, rocks, and open creeks are still a concern.
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.