Be extra cautious around south slopes: they're weak, wind-loaded, and getting hit by the sun.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain
Weather Forecast
TUESDAY: Sunny with cloudy periods, light northeast winds, alpine temperatures around -22.WEDNESDAY: Mix of sun and cloud, light north winds, alpine temperatures around -18.THURSDAY: Mix of sun and cloud, light northwest winds, alpine temperatures around -18.
Avalanche Summary
On Sunday, isolated natural wind slab activity was reported on lee and cross loaded features in the size 1-2 range. Expect wind slabs to remain reactive to human triggers this week, especially on sun-exposed slopes. Also be aware that wind-loading and solar radiation may also make the persistent slab over the mid-December interface reactive in thin snowpack areas.
Snowpack Summary
Strong winds on Sunday had an extensive effect in exposed terrain at all elevations. Expect scouring, hard wind slabs, and thicker reactive wind slabs in unusual places as the winds shifted from west to northeast. Sunny weather is likely making the wind slabs extra touchy on south-facing slopes. The mid-December facet/surface hoar layer can be found buried 40-80 cm deep. This layer has shown signs of being poorly bonded to the overlying slab in snowpack tests, and has produced intermittent avalanche activity in shallow snowpack areas. The lower snowpack is well bonded and features a thick rain crust near the ground that appears to be dormant.
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.