Avalanche Forecast

Issued: Jan 2nd, 2018 6:10PM

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

Avalanche Canada mgrist, Avalanche Canada

We're into a tricky period as a critical amount of storm snow settles (into a slab) and sits on a buried weak layer. Keep your terrain choices on the conservative side until conditions stabilize.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Dry with gradually warming alpine temperatures during the week. Cold in the valley bottoms. WEDNESDAY: Cloudy with sunny breaks. Ridge wind light west. Alpine temperature -5. Freezing level surface.THURSDAY: Mix of sun and cloud. Ridge wind light southwest. Alpine temperature -5. Freezing level surface.FRIDAY: Cloudy with isolated flurries. Ridge wind light west. Alpine temperature -3. Freezing level surface.

Avalanche Summary

We've had several natural avalanches (and the greatest concern) between 1600m and 1800m on steep or open glades on all aspects... this is where the mid December layer has been most active. On Tuesday we had reports of several small loose avalanches triggered by the sun and warmer temperatures in the alpine. On Sunday we had reports of small features being reactive to sled cutting. See here for the MIN report - great information from a low-consequence slope. On Sunday, an explosives-triggered Size 2.5 persistent slab avalanche was reported on a south east aspect at 1700m near Fernie, running on the mid-December surface hoar layer (down 65cm in that location).

Snowpack Summary

The mid-December layer (with variable distribution, but commonly found between 1600m and 1800m) is now buried 40-70 cm below the surface. This layer includes crusts on south and west facing slopes and feathery surface hoar in sheltered areas at and below treeline, and has been producing moderate, sudden results in recent snowpack tests.At higher elevations, winds (at times strong from the south west) have modified the snow pack, creating an "upside-down" slab layer with stiffer snow on top of softer snow.The lower snowpack is generally well settled with a thick prominent crust that was buried near the end of November.

Problems

Persistent Slabs

An icon showing Persistent Slabs
A weak layer composed of surface hoar and/or crusts is buried 40-70 cm below the surface. This layer continues to be very reactive to human triggers and may not improve anytime soon.
Use caution on open slopes and convex rolls at treeline where buried surface hoar may be preserved.Choose well supported terrain without convexities.Watch for whumpfing, hollow sounds, and shooting cracks.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Wind Slabs

An icon showing Wind Slabs
Moderate winds have created fresh wind slabs in the alpine.
If triggered, the wind slabs may step down to deeper layers resulting in large avalanches.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Avoid freshly wind loaded features.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Jan 3rd, 2018 2:00PM

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