Avalanche forecast

Northwest Coastal

Apr 3 – 4, 2014Avalanche Canada
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Avalanche danger

Sat
Sun
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–5
    New snow driven by strong ridge top winds has likely created touchy slabs at and above treeline. This snow is not expected to bond well to the current crust/surface hoar combo and will likely remain sensitive to human triggering Friday.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    3–7
    Two buried weak layers exist in the snowpack. These weak layers could be activated by cornice fall, a smaller surface avalanche in motion, or a rider finding the sweet spot, which would be most likely in steep rocky terrain.

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Synopsis: Friday looks cool and dry, and then a series of weak systems should deliver small amounts of precipitation through the weekend. There's potential for significant precipitation, extreme winds and freezing levels in excess of 2000m beginning Sunday night.Friday: Freezing Level: 700 - 1100m Precipitation: Trace; Wind: Treeline: Light, SW | Ridgetop: Moderate, SWSaturday: Freezing Level: 900m - 1300m; Precipitation: 1:10mm - 1:15cm; Wind: Treeline: Moderate, S/SW | Ridgetop: Strong, SWSunday: Freezing Level: 1000m - 1200m; Precipitation: Trace; Wind: Treeline: Moderate, SW | Ridgetop: Strong, W/SW

Avalanche Summary

No new avalanche activity to report from Wednesday. I suspect that activity ramped up Thursday, look for details in tomorrow's discussion.On Tuesday there was one report of a remotely triggered size 2 wind slab avalanche on a NE facing aspect at 1500m. This location had previously slid on the early February crust/facet/surface hoar combo. Isolated loose wet avalanches to size 1.5 were also reported from steep southerly terrain.On Monday a large rock fall event initiated a size 3.5 avalanche that failed on the early February persistent weak layer. Several smaller loose snow avalanches to size 2 were running in the recent storm snow on steep solar aspects too.

Snowpack Summary

The storm has produced 15 - 25cm of new snow as of Thursday afternoon. This snow rests on surface hoar, small grained facets and melt freeze crusts.Previous to Thursday's snow, it was starting to feel like spring in the NW. Valley temps have been creeping into the double digits during the day, and there are reports of the top 15 cm of the snowpack regularly becoming moist with daytime heating.Prior to the snowfall Thursday, the last significant shot of snow was on March 27th, another 10 - 15 fell on March 30th. This old storm snow rests on top of a haggard old surface composed of old wind slab, melt freeze crust, and faceted old snow. I suspect the ongoing melt freeze cycles have largely healed any instabilities associated with this interface.The early March layer can be found down 75 - 100cm and is composed of facets/surface hoar on shady aspects and facets/crust on southerly aspects. The early February crust/facet/surface hoar combo is down 150 - 200cm, and I suspect it's gone mostly dormant for now.

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