Avalanche Forecast South Rockies

Tuesday 5th February 2019

Avalanche Danger Ratings Tue 5th Feb 4:53PM Danger Ratings Alpine: Moderate Danger Ratings Treeline: Moderate Danger Ratings Below Treeline: Moderate Persistent Slabs Persistent Slabs Wind Slabs Wind Slabs Deep Persistent Slabs Deep Persistent Slabs

Avalanche Canada Forecaster: cgarritty

Date Issued:

Valid Until:

Use visible patterns of wind loading to steer you away from unstable pockets of wind slab. Persistent slabs don't offer these clues, so seek out low consequence slopes in areas where buried surface hoar exists and keep avoiding thin snowpack areas.

Confidence

Moderate -

Weather Forecast

Tuesday night: Cloudy with clear periods. Light northeast winds. Wednesday: Mainly sunny. Light northeast winds, increasing to moderate in the alpine. Alpine high temperatures around -19.Thursday: A mix of sun and cloud with cloud increasing over the day. Light southwest winds, increasing to moderate in the alpine. Alpine high temperatures around -15.Friday: Mainly cloudy with isolated flurries and a trace of new snow. Light northeast winds. Alpine high temperatures around -20.

Avalanche Summary

No new avalanches were reported on Sunday.Many small to large avalanches were triggered within the recent storm snow by skiers, naturally, and with explosives on Saturday. The fact that we have numerous weak layers within our snowpack indicates that conservative decisions should be made at this time.

Snowpack Summary

Above 1700 m, 25 to 35 cm of recent snow overlies a variety of surfaces, including feathery surface hoar crystals in shaded and sheltered areas, wind-affected snow in exposed terrain, and a melt-freeze crust on southerly aspects. Below 1700 m, expect to find around 5-10 cm of low-density snow on a melt-freeze crust.The mid-January layer of surface hoar or a crust is buried around 35 to 45 cm deep. The surface hoar is found on shaded and sheltered slopes and is most prominent between 1600 m and 1900 m but has been found up to 2100 m. The melt-freeze crust is found on south aspects at all elevations.The middle of the snowpack is generally consolidated. The bottom half of the snowpack is unconsolidated and composed of weak and sugary faceted grains.

Persistent Slabs Persistent Slabs

Likelihood

Likely - Possible

Expected Size

1.5 - 2.5

The recent storm has put a weak layer of surface hoar (now buried 40 to 60 cm deep) under a critical load. This surface hoar is best preserved in shaded, sheltered areas between 1600-1900 m. On south aspects, the surface hoar may coexist with a crust

Be aware of the potential for large avalanches due to the presence of buried surface hoar.Be aware of the potential for wide propagation.Use added caution in open terrain features, such as cutblocks, gullies, and cutbanks.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

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Wind Slabs Wind Slabs

Likelihood

Possible

Expected Size

1 - 2

Recent snow may have been redeposited with southwest winds that switched to northeast winds. The touchiest pockets will likely be adjacent to ridges.

Be careful with wind-loaded pockets, especially near ridge crests and roll-overs.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Good day to make conservative terrain choices.

Aspects: All aspects.

Elevations: Alpine, Treeline.

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Deep Persistent Slabs Deep Persistent Slabs

Likelihood

Possible - Unlikely

Expected Size

2 - 3.5

The bottom of the snowpack consists of weak and sugary faceted snow. The consequences of triggering this layer remains high, as avalanches will be large and destructive.

Use conservative route selection, such as moderate-angled and smooth terrain with low consequence.Watch for signs of instability such as whumpfing, cracking, or recent avalanches.Avoid steep, rocky terrain and shallow snowpack areas where triggering deep layers is more likely.

Aspects: All aspects.

Elevations: All elevations.

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