A Special Public Avalanche Warning (SPAW) has been issued for the region. The concern is the unusually slow bonding within the entire snowpack. Recent slab avalanches have been large and in many cases very surprising.
Weather Forecast
Saturday will be very similar to today. The temps today exceeded the forecasted values, so we can expect something similar tomorrow. Sunny periods are expected, solar heating could be an issue on south aspects. The forecasted freezing level is 2000 with a 2500m high of -2. The 2500m winds should be steady at 40km/hr from the NW. No snow (or rain) is expected.
Avalanche Summary
A bombing mission on Rundle had limited results. 3 of the 4 bombs produced avalanches up to sz2. All of them failed on the Jan31st layer. Previous control had dealt with the deeper layers, so these results are not necessarily transferable to the backcountry.
Snowpack Summary
Today's temperatures reached well above zero in all forecast areas. The Aster Lake region hit +3 degrees. The lack of an overnight freeze left the valley bottom snow isothermal in places. This condition gradually improves with elevation, but generally the snow up to treeline has had significant warming. Treeline and above has windslabs that are dense, and relatively warm. Whumphing is less common now, but the weak interface is still present. The Jan31st interface is still the main concern at all elevations. At treeline it is down 50-60.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.