Avalanche Forecast

Issued: Feb 24th, 2019 3:53PM

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

dsaly, Avalanche Canada

Lizard-Flathead.

Expect continued slab development and reactivity as the new snow settles and is affected by wind.

Summary

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

SUNDAY NIGHT: Clear. Alpine temperatures near -25C. Ridgetop winds moderate from the east.MONDAY: Sunny with increasing cloud and isolated flurries in the evening, up to 5 cm. Alpine temperatures near -20C. Ridgetop winds moderate from the east-northeast.TUESDAY: Mix of sun and cloud, isolated flurries. Alpine temperatures near -22C. Ridgetop winds moderate from the northeast.WEDNESDAY: Sunny with cloudy periods. Alpine temperatures near -15C. Ridgetop winds light from the east-northeast.

Avalanche Summary

On Sunday, a skier triggered a size 1 storm slab avalanche on a north aspect around 2100 m. On Saturday, numerous natural and explosives triggered storm slab avalanches to size 2-2.5 were reported. These were 50-100 cm deep running on east through north aspects in the alpine and treeline. Loose, dry snow is sloughing in steeper terrain. Last Thursday, an explosive triggered a large (size 2.5) persistent slab avalanche. The slab was about 40 cm deep and failed on a southerly aspect between 1650 and 2000 m.

Snowpack Summary

Up to 60 cm low density new snow is settling out and being redistributed by wind. The new snow sits on wind affected surfaces in the alpine and treeline. In sheltered areas, the new snow is burying faceted surface snow and possibly a layer of surface hoar. In sheltered areas between 1600 and 1800 m, another weak layer of surface hoar crystals buried around Valentines Day, is now 60-80 cm below the snow surface.Two more weak layers of surface hoar may be found within the snowpack. One buried early-February, is 80-100 cm deep in shaded and sheltered areas above 1600 m. The other buried mid-January, is 100-150 cm down and is most prominent between 1600 m and 1900 m.The remainder of the snowpack is well-settled.

Problems

Wind Slabs

Up to 60 cm of low density new snow accumulated into Saturday. Expect this new snow to continue to be reactive as a storm slab as it settles and is influenced by east-northeasterly winds.

If triggered, storm or wind slabs may step down to deeper layers resulting in large avalanches.Keep an eye out for reverse loading created by variable winds.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

Two weak layers of surface hoar may be found between 1500 m and 1900 m, around 80-120 cm deep in the snowpack. These layers have been the culprit of recent large avalanches, particularly in openings such as cutblocks, gullies, and slide paths.

Be aware of the potential for wide propagation.Watch for signs of instability such as whumpfing, cracking, or recent avalanches.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Feb 25th, 2019 2:00PM