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Avalanche Forecast

Archived

Feb 13th, 2019–Feb 14th, 2019

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

Regions

Kootenay Boundary.

The region has picked up significant new snow and the trees are not the safe haven they normally are. With two buried surface hoar layers in play it's time to stick to simple, well-supported terrain where you'll find great riding.

Confidence

Low - Timing, track, or intensity of incoming weather system is uncertain on Friday

Weather Forecast

The current weather pattern is very complex, and the weather models are not in agreement. As of Thursday afternoon most of the models suggest that precipitation amounts will be light across the Kootenay Boundary through the weekend, but these amounts could easily double if the storm tracks just a smidge further north than what's currently anticipated. With all of this uncertainty it's very difficult to pin down precipitation amounts which is why the ranges are so significant below. Stay tuned for more details. WEDNESDAY NIGHT: Skies clearing through the night, freezing level at valley bottom, around -10 C in the alpine, light variable wind, no significant snowfall expected.THURSDAY: Clear skies in the morning building to overcast in the late afternoon, freezing level creeping up to 900 m during the day, light to moderate east/southeast wind, 1 to 4 cm of snow possible in the afternoon. 2 to 10 cm of snow possible Thursday night.FRIDAY: Overcast, freezing level should be near valley bottom, light southwest wind, 3 to 10 cm of snow possible.SATURDAY: Overcast, freezing level should be near valley bottom, light northwest wind, 1 to 5 cm of snow possible.

Avalanche Summary

Early reports from Wednesday indicate that natural storm slab avalanches to size 2 were once again widespread. Stay tuned for more details tomorrow. On Tuesday storm slab avalanches were widespread to size 2 on all aspects/elevations. The storm slabs were very touchy, and some were remote triggered from as far as 50 m away. Loose dry sluffs were also reportedly very touchy as indicated in this MIN report.

Snowpack Summary

25 to 40 cm of storm snow has formed a slab that rests on a variety of old surfaces that include a sun crust on southerly aspects to mountain top, variable wind affected snow and weak feathery surface hoar crystals at and below treeline. The snowpack now hosts two buried surface hoar layers. The February 1st surface hoar is down 40 to 60 cm and has been recently reactive to human triggers. The mid-January surface hoar is 60 to 100 cm below the surface. This deeper layer of surface hoar is most prevalent below treeline on shady aspects but it does not seem to be a widespread problem in the region. Below that, the snowpack is well settled.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.