Avalanche forecast

South Rockies

Feb 28 – 29, 2012Avalanche Canada
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Avalanche danger

Thu
Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4
    Winds are forecast to be out of the SW Wednesday with enough velocity to create fresh windslabs. With all of the new snow available for transport, skiers & riders will need to stay alert for fresh slab development in wind exposed terrain.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–7
    The weak layer of buried surface hoar, facets, and crusts remains a concern for backcountry skiers & riders. Avalanches are expected to get larger as the slab above settles and consolidates. This weak layer may propagate into low angle terrain.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    Light dry snow that fell over the past few days has been sluffing in steep terrain, running far and fast. Wednesday's 5 - 10cm of storm snow will likely react in a similar fashion.

Confidence

Fair - Intensity of incoming weather is uncertain on Wednesday

Weather Forecast

A low pressure system is tracking south of the international border Wednesday which will result in about 5 -10 cm of snow which will continue through Wednesday night. Winds will be near 40 km/h at 2000m Wednesday, which is more than enough to move snow. Wed. 1500m Temp: H: -3, L: -9. Thursday looks to be more of the same as the So. Rockies receive a bit of upslope activity on the east slopes in the early morning. This activity will taper mid-morning as winds shift to the NW and diminish to light values. On Friday, the ridge of high pressure off the coast of BC flattens allowing for a more zonal pattern for the weekend, which means a few cm of snow each day both Saturday and Sunday.

Avalanche Summary

Our field team observed an avalanche failing on a steep bluff, the SH was assumed to be the weak layer. No other reports of avalanches from this region, but that doesn't mean they aren't happening. It's important to remember that this region is often quite data sparse.

Snowpack Summary

Saturday night into Sunday, moisture in the west of the region collided with cold air in the east and resulted in an intense period of heavy snowfall that was very low density. This new snow has likely settled a bit with daytime warming Monday. Now 50-60 cm of recent snow sits on a reactive weak layer of crusts, surface hoar and facets. Our field team was in the Elk Valley North sub region, operating between 2000 & 2300m. They reported weaknesses failing with moderate to hard shears down 60 cm. It will be interesting to see what kind of results they get from their field days in the next 72 hours. For the moment, we can assume that there is a slab of approx. 60 cm in depth in most of the region that is still prone to human triggering. Below this, the mid-pack is quite strong in most locations. However, lingering concern remains for basal facets, particularly in shallower snowpack areas with steep, rocky start zones.

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