North winds have reversed the typical loading pattern and have made windslabs in unusual places. On top of this, cornice growth has changed the overhead exposure risk. Take a good look around before setting off.
Weather Forecast
We'll see a brief break in the winds tomorrow. They will average 20km/hr, but occasionally gust to 45. They are also expected to swing around to the SW overnight. The temp will be -1 in the alpine, with near zero temps expected valley bottom. The cloud cover will help limit the solar input.
Avalanche Summary
The south end of the Goat Range had 1 sz2.5 slab that released in the last 12 hours. 2500m, NE asp, initiated out of thin cliff bands and scrubbed to ground low in the start zone. Re-loading from the wind has essentially erased all evidence of yesterday's cycle.
Snowpack Summary
Wind is the story with our snowpack. Even below treeline has seen some wind affect in the last 24-36hrs. In many areas the crust has been blown clean and is back on the surface. In sheltered areas, expect the Feb 11th crust to be down 10-15cm. Treeline is either wind scoured or new, reverse loaded windslabs. There are still sheltered areas just below treeline with good snow, but the north winds have made them few and far between. In sheltered areas the feb 11th crust is down 20-30cm with new windslabs sitting on top. The alpine elevations have seen sustained north/northwest winds that have created widespread windslabs.
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.