Avalanche Forecast

An unsettled weather pattern will bring light to moderate snowfall amounts and strong ridgetop wind through the weekend.

Wednesday Overnight: New snow 5-15 cm by mid-morning on Thursday. Freezing level dropping to valley bottom. Alpine temperatures -10 and strong West to northwesterly winds. 

Thursday: Snow amounts 5-15 cm. Freezing level rising to 1500 m. Alpine temperature near -5 with strong northwesterly wind. 

Friday: Snow 5-10 cm. Freezing level rising to 1500 m and alpine temperatures near -5. Strong West wind. 

Saturday: Snow 5-10 cm. Freezing level 1100 m and alpine temperature near -8. Moderate southwest wind.   

If you see more than 20 cm of fresh snow expect to see some reactive storm slabs and deeper wind slab on leeward slopes and terrain features. 

On Tuesday, a natural cornice fall triggered a persistent slab size 2.5 from an East aspect at 2000 m. This was said to be approximately 72 hours old. On Monday, a natural cornice fall size 1.5 was reported and did not pull a slab from the slope below. The aspect and elevation are unknown. 

Last Friday, sledders near Blue River remote triggered several large slab avalanches on shaded aspects at treeline. The failure plane of these avalanches is uncertain, but large remote triggered avalanches would make us suspect it failed on the late January buried surface hoar. Photos from this incident can be seen here.

As a result of the rain event last Wednesday (a week ago), operators in the north of the region observed a large natural avalanche that initiated as a storm slab in the alpine and gouged to ground lower down in the track in wet, uncohesive snow.

Up to 15 cm of new snow fell by Wednesday morning and is expected to bond poorly to the old surface. This surface is comprised of near-surface faceting and in some areas, surface hoar growth overlying a melt-freeze crust at lower elevations, a sun-crust on steep solar aspects, and hard wind-affected snow in the alpine and exposed treeline. 

Several weak layers exist in the upper snowpack including buried crusts, facets, and a prominent weak layer of surface hoar. This surface hoar is the dominating feature. It was buried in late January and exists 40 to 100 cm deep in the snowpack. Reports suggest that the surface hoar is most prominent in sheltered openings at and below treeline. Terrain features to be suspect of includes the lee side of protected ridges, openings in the trees, cut blocks, and burns. 

The lower snowpack is generally strong and well-bonded.

• Use increased caution at all elevations. Storm snow is forming touchy slabs.
• Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
• Be aware of the potential for large avalanches due to the presence of buried surface hoar.
• Surface hoar distribution is highly variable. Avoid generalizing your observations.