Avalanche Forecast

Issued: Jan 31st, 2020 5:00PM

The alpine rating is high, the treeline rating is high, and the below treeline rating is high. Known problems include Loose Wet and Storm Slabs.

Avalanche Canada istorm, Avalanche Canada

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WIth the forecast storm avalanche hazard will rapidly rise to HIGH on Saturday. A widespread natural avalanche cycle is expected at all elevations.

Summary

Confidence

High - We are confident a natural avalanche cycle will begin shortly after the arrival of the incoming weather.

Weather Forecast

Friday Overnight: Warm, wet, intense storm ramping up. Freezing level rising to 2000m. Strong southwest wind. Precipitation of 15 to 30 mm water equivalency. Normally that means 20 to 60 cm of snow; with this storm it means soaking rain at lower elevations and up to 30 cm of snow at the highest elevations.

Saturday: Freezing levels lowering with temperatures falling back below freezing by end of day. 5 to 15 mm of water equivalent translates into, depending on your elevation: rain, a mix of rain & snow, or up to 15 cm of snow. Strong west winds.

Sunday: Mix of sun and cloud. Flurries for most of the region but up to 10 cm of snow in western upslope locations. Temperatures have cooled down to around -10 C in the mountains with moderate northwest winds

Monday: Dry. Mix of sun and cloud. Temperatures steady around -1- to -15 C. West to northwest wind at moderate strength.

Avalanche Summary

WIndslabs continue to be reported throughout the region, with this MIN report (with great photo) being a good example of the type of problem we're dealing with. Recent ones were in the size 1 to 1.5 range.

Looking forward, a warm wet storm will create a Loose Wet avalanches at lower elevations and increase the likelihood of Storm Slabs (and Wind Slabs) at higher elevations.

Snowpack Summary

Here's a snowpack description as of Friday Jan 31 before the forecast warm wet "atmospheric river" (previously know as a pineapple express) storm arrives. This description will obviously no longer apply once hit by soaking rain at lower elevations .... The upper snowpack is right-side-up meaning light dry & fluffy (aka powder) at the surface which gradually blends into increasingly harder and stronger snow with depth.The weeks-long weather pattern of snow & wind also means there are widespread storm and wind slabs.

In the mid-pack there's a layer of weaker surface hoar buried in late December that remains a concern but is gaining strength. This layer is found across much of the North Rockies region but our focus is around McBride and the McGregors/Torpy. It's a classic surface hoar layer that's most prominent in sheltered treeline features 50 to 150 cm below the surface.

Terrain and Travel

  • Watch for rapidly changing conditions during periods of heavy loading from new snow, wind, or rain.
  • Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
  • Loose avalanches may start small but they can grow and push you into dangerous terrain.

Problems

Loose Wet

An icon showing Loose Wet

With freezing level rising to near 2000 m there will be soaking rain at lower elevations. A Wet Loose avalanche cycle is expected.

Aspects: All aspects.

Elevations: Below Treeline.

Likelihood

Very Likely

Expected Size

1 - 2.5

Storm Slabs

An icon showing Storm Slabs

With a warm wet storm the snowpack will turn upside-down creating a widespread storm slab problem. Strong winds will build windslabs at higher elevations where the snow is dry enough to be blown into deeper slabby pillows. 

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1.5 - 3

Valid until: Feb 3rd, 2020 5:00PM

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