Avalanche Forecast

Issued: Mar 26th, 2018 4:55PM

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

cgarritty, Avalanche Canada

Lizard-Flathead.

Strong winds are forecast to peak on Tuesday. Expect widespread wind slab formation and watch for rising freezing levels to make slabs and cornices increasingly touchy.

Summary

Confidence

Moderate -

Weather Forecast

Tuesday: Cloudy with flurries, together with overnight flurries bringing 5-10 cm of new snow. Strong to extreme southwest winds. Freezing level rising to 1600 metres after weak overnight cooling with alpine high temperatures around -3.Wednesday: A mix of sun and cloud. Moderate northwest winds. Freezing level to 1500 metres after weak overnight cooling with alpine high temperatures around -4.Thursday: A mix of sun and cloud, with cloud increasing over the day and flurries beginning in the afternoon. Light west winds. Freezing level to 1600 metres with alpine high temperatures around -3.

Avalanche Summary

Two more natural cornice releases were observed triggering size 2 storm slabs in the Fernie area on Monday.Reports from Sunday included numerous observations of recent large (size 2-2.5) natural storm slab releases in the Fernie area. Another round of explosives control yielded similar results, with slab depths generally from 30-70 cm. All but southwest aspects showed activity above 1800 metres and northeast aspects were the most active. Two natural cornice releases were also observed triggering slabs on the slopes they landed on.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.

Snowpack Summary

Up to 50 cm of recent storm snow has been showing a poor bond to the old snow surfaces it has buried, including a melt-freeze crust on sunny aspects and all aspects below 1600 m as well as 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 considered dormant.

Problems

Wind Slabs

Increasingly strong southwest winds are are continuing to redistribute our storm snow into reactive wind slabs. Slabs may also be reactive in steeper, sheltered areas where the recent snow sits on crust or surface hoar.

Wind slabs may be more reactive where they sit on a buried crust or surface hoar interfaceUse ridges or ribs to avoid pockets of wind loaded snow.Use extra caution on slopes if the snow becomes moist or wet with rising daytime temperatures.

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. Natural cornice falls have recently been observed triggering slab avalanches.

Pay attention to overhead hazards like cornices which could trigger slabs on slopes below.Give cornices a wide berth when travelling on or below ridges.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Valid until: Mar 27th, 2018 2:00PM