http://www.pc.gc.ca/apps/links/goto_e.asp?destination=http://data.avalanche.ca/Images/SPAW%20Feb%207%202019.pdfA Special avalanche warning is in effect. Dangerous avalanche conditions exist at and below treeline where a weak layer of preserved surface hoar lingers. Careful route selection is essential, even at lower elevations.
Weather Forecast
Cold temperatures will persist into the foreseeable future. Mainly Cloudy today with isolated flurries and trace amounts of precipitation. The alpine temperature will climb to -17 with freezing levels remaining at valley bottom. Ridge winds from the NE, 12-25 km/h.
Snowpack Summary
A thin sun crust has formed on steep solar aspects in the alpine. Cold temperatures are promoting near surface faceting and softening wind slabs that exist in alpine and exposed areas at tree line. The storm snow has settled has to ~50cm. The Jan 31 and Jan 17 interfaces (surface hoar and sun crust) are down ~50cm and ~70cm at tree line.
Avalanche Summary
No new avalanches were observed yesterday.
Problems
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.
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.