Avalanche Forecast
Issued: Jan 4th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
ahanna,
Avalanche Canada
There is some uncertainty as to how the recent storm snow is bonding to the old surface and how buried weak layers have reacted under the new load.
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Summary
Confidence
Low - Uncertainty is due to the limited number of field observations.
Weather Forecast
Saturday night: Flurries accumulating 10-15 cm, strong southwest wind, alpine high temperatures around -8 C.
Sunday: Flurries accumulating 5-10 cm, moderate west wind, alpine high temperatures around -12 C.
Monday: Mix of sun and cloud with isolated flurries, light southeastt wind, alpine high temperatures around -10 C.
Tuesday: Mix of sun and cloud with isolated flurries, light variable wind, alpine high temperatures around -10 C.
Avalanche Summary
A widespread avalanche cycle up to size 3 was reported from the Howson range during the storm on Friday. This cycle is likely to have occurred throughout the southern part of the region where more than 40 cm of snow fell on Friday.Â
Before the storm, reports of persistent slab avalanches associated with buried surface hoar were trickling in, from Ashman, Telkwa and Howson areas. They included natural and artificially triggered avalanches ranging in size from 1.5-3, and have occurred on all aspects mainly at treeline but also in the alpine. The new snow load will increase the size and consequences of avalanches on these layers.
Snowpack Summary
Flurries overnight and into Sunday will bring storm snow depths to 40-50 cm. In the alpine, the storm snow has likely been highly wind affected. Expect to find deep wind loaded pockets below ridgetops and the lee sides of exposed features. Below treeline, soft, unconsolidated snow can be found at low elevations amid cool temperatures.
A couple of layers of surface hoar are now buried 50-100 cm below the surface in sheltered areas around treeline. Reports of avalanche activity on these layers suggest they have recently become active, and the new snow load will provide additional stress.
Terrain and Travel
- Closely monitor how the new snow is bonding to the old surface.
- Give the new snow several days to settle and stabilize before pushing into bigger terrain.
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
Problems
Storm Slabs
Overnight flurries will bring storm snow depths to 40-60 cm. Strong winds have likely formed deep pockets of storm slab in lee features in the alpine and treeline. There is uncertainty as to how the storm snow is bonding to the old surface.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A couple layers of surface hoar are now buried 50-100cm deep, with uncertainty around their distribution outside of the treeline elevation band. There is uncertainty as to how the buried weak layers have reacted to the new load of storm snow. Human triggering of weak layers at this depth is definitely possible and would result in large, high consequence avalanches.
Aspects: All aspects.
Elevations: Treeline.
Likelihood
Expected Size
Valid until: Jan 5th, 2020 5:00PM
