Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Feb 10th, 2013–Feb 11th, 2013

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

South Columbia.

Confidence

Fair - Timing of incoming weather is uncertain on Tuesday

Weather Forecast

Monday: The pattern and flow will start to change today as the ridge moves southward and a zonal flow sets up. An embedded cold front will move through the region bringing moderate West winds and a trace of snow. Treeline temperatures will sit near -3 and freezing levels will be around 1100 m. Tuesday: The fast paced zonal flow will continue with a trough moving in from the West bringing moderate Westerly winds and light-moderate snow accumulations. Westerly upslope areas may see more accumulations. Treeline temperatures will be near -5 and freezing levels around 1100 m.Wednesday: Another ridge is building bringing dryer conditions; especially for the short term. Ridgetop winds moderate from the SW. Treeline temperatures -9 and freezing levels near 700 m falling to valley bottom overnight.  

Avalanche Summary

On Saturday, several natural slab avalanches up to size 2.5 were reported from steep slopes on a variety of aspects 1700 m and above. Suspect failing layer was the early Feb surface hoar/crust and triggered by wind. Several rider triggered avalanches were reported up to size 2 above 1900 m on most aspects and the early Feb interface being the main culprit.

Snowpack Summary

Up to 40 cm of new snow adds to the recent storm slab which sits on a surface hoar layer and a sun crust layer that developed at the beginning of February. This layer continues to be reactive to rider triggers. Deeper down (between 40-80 cm) sits an old sun crust and well preserved surface hoar that was buried on January 23rd. This persistent slab has been reactive over the past few days, especially from solar aspects. Recent snowpack tests on this layer have shown moderate compression results with sudden planar to resistant planar characteristics. Wind slabs exist in specific locations in the alpine and at treeline. The loading pattern may change due to winds switching from the SW to the NW and form pockets of wind slab in unsuspecting places.The mid-pack is well settled and strong. Cornices loom and threaten slopes below.

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.