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

Dec 15th, 2018–Dec 16th, 2018

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

Regions

Purcells.

A Special Public Avalanche Warning (SPAW) is in effect for this region. Natural avalanche activity has decreased to some degree, but THE POTENTIAL FOR HUMAN TRIGGERED AVALANCHES REMAINS LIKELY.

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

SATURDAY NIGHT - Mainly cloudy with isolated flurries / south to southwest winds, 25-35 km/h / alpine low temperature near -10SUNDAY - Mainly cloudy with flurries, 5 cm / south to southwest winds, 15-40 km/h / freezing level 1700 m / alpine high temperature near -2MONDAY - Flurries, 5-15 cm / southwest winds, 20-40 km/h, gusting to 55 km/h / freezing level 1600 m / alpine high temperature near -2, low temperature near -5TUESDAY - Snow, 15-15 cm / southwest winds, 25-45 km/h, gusting to 65 km/h / freezing level 1500 m / alpine high temperature near -4, low temperature near -6

Avalanche Summary

Avalanche activity has been extensive in the Purcells, continuing through Saturday with reports of both human and explosive triggered avalanches to size 3. One very notable report on Saturday was a size 2.5 human triggered avalanche that was remotely triggered from 50-100 m away on a northwest aspect at 2250 m. A report of this avalanche can be found on the Mountain Information Network. (here)Numerous human and explosives avalanches up to size 3.5 were reported on Friday. Several of these were remote triggered. (triggered from a distance)A natural avalanche cycle to size 4 was also reported in the region on Friday.

Snowpack Summary

60-100 cm of snow sits on a weak layer of facets (sugary snow), surface hoar (feathery crystals), and a sun crust (on south facing slopes). Strong winds have promoted widespread slab formation.Another layer of surface hoar and sun crust is now buried 100-150 cm. The potential may exist for smaller avalanches to step down to this deeper layer, resulting in very large avalanches. The most likely areas for this layer to be a problem is where the surface hoar sits on the sun crust, which is most likely on steep south facing terrain at treeline.At the base of the snowpack is a crust that formed in late October. This layer is likely only a problem on large, steep alpine features with a shallow snowpack. It likely take a large trigger, such as a cornice fall, to produce an avalanche on this layer.

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.