Avalanche Forecast

Issued: Jan 25th, 2018 5:14PM

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.

jmcbride, Avalanche Canada

South Rockies.

Recent storm snow and wind are adding to a snowpack with several buried weak layers. Best to stick to conservative terrain, avoid wind-loaded areas, and back off if you see classic warming signs like whumpfing or cracking.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

TONIGHT: Mostly clear. Ridge wind strong, southwest. Temperature -10. Freezing level lowering to valley bottom.FRIDAY: Mix of sun and cloud, light flurries. Accumulation trace. Ridge wind moderate to strong, west. Temperature -5. Freezing level valley bottom.SATURDAY: Cloudy, flurries. Accumulation up to 2 cm. Ridge wind light, south. Temperature -5. Freezing level valley bottom.SUNDAY: Cloudy, flurries. Accumulation up to 2 cm. Ridge wind moderate, southwest. Temperature -4. Freezing level 500 m.

Avalanche Summary

On Thursday explosive control work in the Castle area triggered a Size 3 avalanche from a shallow area that propagated and failed on the late-November layer deep in the snowpack. While in the Bull River area a natural Size 2 was observed on west-facing cutblock at 1600 m.The lack of activity can most likely be attributed to a lack of observations rather than snowpack conditions. The snowpack in the region remains suspect with several buried weak layers displaying classic signs of instability such as whumpfing and cracking.A recent video posted to the Avalanche Canada South Rockies field team Facebook page paints a pretty clear picture https://www.facebook.com/avcansouthrockies/videos/1894352117306941/.

Snowpack Summary

Up to 30 cm of recent storm snow now covers both a new layer of feathery surface hoar in sheltered areas as well as sun crust on solar aspects buried mid-January, and about 30-50 cm below the surfaces lies the early-January surface hoar layer.About 60-80 cm below the surface a weak layer of feathery surface hoar crystals and/or sun crust buried mid-December is found at treeline and below treeline elevations. Near the base of the snowpack the weak early-season layer of rain crust and sugary facets buried late-November exists. Although the snowpack structure is variable across the region, these persistent weak layers are generally widespread. Snowpack depths are also variable across the region and typically thinner in northern areas than in areas to the south.

Problems

Wind Slabs

Winds have created wind slabs in leeward areas near ridge crest in the alpine and in exposed treeline areas. A release near the surface has the potential to step down to a deeper layer.

If triggered, wind slabs may step down to deeper layers and result in large avalanches.Use caution in lee areas in the alpine and treeline. Wind and storm snow are forming touchy slabs.

Aspects: North, North East, East, South East, South.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

Several weak layers of concern are buried within the snowpack and have the potential to produce large avalanches. Conservative terrain with moderate-angled, supported slopes are good choices.

Watch for signs of instability such as whumpfing, or shooting cracks.Be aware of thin snowpack areas where deeper weak layers may be more sensitive to triggering.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1.5 - 3

Valid until: Jan 26th, 2018 2:00PM