Avalanche Forecast

Issued: Mar 25th, 2018 4:47PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Wind Slabs and Cornices.

cgarritty, Avalanche Canada

Lizard-Flathead.

Strong winds will maintain touchy conditions on Monday. Keep seeking out supported lines in sheltered areas while the storm snow settles and bonds.

Summary

Confidence

Moderate -

Weather Forecast

Sunday night: Scattered flurries bringing a trace to 5 cm of new snow. Moderate to strong southwest winds.Monday: Mainly cloudy with isolated flurries and a trace of new snow, increasing overnight. Strong southwest winds. Freezing level to 1300 metres with alpine high temperatures around -5.Tuesday: Cloudy with scattered flurries bringing around 2 cm of new snow, increasing overnight. Strong to extreme southwest winds. Freezing level rising to 1800 metres after a poor overnight refreeze. Alpine high temperatures around -1.Wednesday: A mix of sun and cloud with continuing scattered flurries bringing a trace to 5 cm of new snow. Moderate westwinds. Freezing level to 1600 metres with alpine high temperatures around -3.

Avalanche Summary

Cornice control on Saturday work gave numerous size 1-2 avalanches on north through southeast ridgelines. above 1900m. The cornice failures produced mostly loose dry avalanches from the slopes below with a few smaller slabs only releasing in the storm snow. On Friday, numerous natural storm slab avalanches were reported from North aspects above 1700 m. Periods of sunshine forecast for Sunday could trigger a round of natural slab avalanches and loose dry/wet avalanches.

Snowpack Summary

Up to 50 cm of recent storm snow will initially have a poor bond to the plethora of old snow surfaces including a melt-freeze crust on sunny aspects and all aspects below 1600 m, surface hoar on north aspects above 1600 m. Wind slabs are building on most aspects due to the changing winds and overhanging cornices exist along ridgelines. Deeper in the snowpack, the mid-December and late-November weak layers are composed of crusts and sugary facets, which are down 150-300 cm. These layers are currently dormant.

Problems

Wind Slabs

Increasingly strong southwest winds are set to press and redistribute our new snow into reactive new wind slabs over Sunday night and Monday. Slabs may also be reactive in steeper, sheltered areas where the recent snow sits on crust or surface hoar.

Use ridges or ribs to avoid pockets of wind loaded snow.Wind slabs may be more reactive where they sit on a buried crust or surface hoar interfaceUse conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 2.5

Cornices

Large looming cornices exist across ridgelines. Cornices are unpredictable and demand respect. They're more likely to fail during wind events or when the sun comes out.

Give cornices a wide berth when travelling on or below ridges.Pay attention to overhead hazards like cornices which could trigger a slab from the slope below.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2.5

Valid until: Mar 26th, 2018 2:00PM