Avalanche Forecast

Issued: Feb 16th, 2019 4:12PM

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

mconlan, Avalanche Canada

Lizard-Flathead.

Recent observations of persistent slab avalanches suggest buried weak layers may be touchy, particularly in openings like cutblocks. Also use caution at higher elevations, since the wind may have turned the recent snow into slabs.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

SATURDAY NIGHT: Cloudy with light snowfall, accumulation 1 to 5 cm, light to moderate northeast wind, alpine temperature -17 C.SUNDAY: Mix of sun and cloud with isolated flurries, trace accumulation, light to moderate northeast wind, alpine temperature -21 C.MONDAY: Mostly clear skies, light to moderate north wind, alpine temperature -18 C.TUESDAY: Partly cloudy skies, light west wind, alpine temperature -16 C.

Avalanche Summary

Widespread large (size 2) persistent slab avalanches were observed in the region on Saturday - check the report out here. The avalanches released on the surface hoar described in the Snowpack Summary. The slabs were 40 to 100 cm deep. They released between 1550 m and 1700 m on north aspects. There was also further evidence of instability within the buried weak layers, as noted here and here.Otherwise, small to large (size 1 to 2) wind, storm, and persistent slabs were triggered by explosives and skiers, all on northerly aspects and around 2000 m. The slabs varied from 5 to 40 cm deep.

Snowpack Summary

Around 10 cm of recent snow overlies a weak layer of surface hoar crystals found between 1600 m and 1800 m. Strong wind may have redistributed this recent snow and formed wind slabs in lee terrain features at higher elevations. The wind was first westerly and switched to northeast, so wind slabs may be found on all aspects.Two weak layers may be found within the snowpack. Surface hoar that was buried early-February may be found about 40 to 50 cm deep in shaded and sheltered areas above 1600 m. The mid-January layer of surface hoar is buried around 70 cm and is most prominent between 1500 m and 1900 m.The remainder of the snowpack is well-settled. Thin snowpack areas, such as in the far east of the region, may have weak and sugary faceted grains near the base of the snowpack.

Problems

Wind Slabs

The recent snow may continue to be reactive to human traffic. Wind was first from the west and shifted to the northeast, which likely moved the recent snow around at higher elevations. Use particular caution in lee terrain features near ridges.

Use caution in freshly wind-loaded features, especially near ridge crests and in steep terrain.If triggered, wind slabs may step down to deeper layers resulting in large avalanches.Keep an eye out for reverse loading due to northeast wind.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

Two weak layers of surface hoar crystals may be found between 1500 m and 1900 m, around 40 to 70 cm deep in the snowpack. These layers have been the culprit of recent large avalanches, particularly in openings such as cutblocks.

Watch for signs of instability such as whumpfing, cracking, or recent avalanches.Make observations and assess conditions continually as you travel.Be aware of the potential for wide propagation.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Valid until: Feb 17th, 2019 2:00PM