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 Wind Slabs.
ahanna,
Avalanche Canada
Strong winds have blown the recent snow into reactive windslab in the alpine and treeline. Avoid fat looking pockets of snow in lee features.
Summary
Confidence
Moderate - Uncertainty is due to the extreme variability of wind effect on the snowpack.
Weather Forecast
Saturday night: Cloudy with clear periods and isolated flurries bringing up to 5 cm, moderate wind from the southwest, alpine low temperature -6 C, freezing level dropping to valley bottom.
Sunday: Cloudy with a trace of snow, light wind from the southwest, alpine high temperature -4 C, freezing level valley bottom.
Monday: Up to 5 cm of snow, light wind from the southwest, alpine high temperature -4 C, freezing level valley bottom.
Tuesday: 10-15 cm of snow, light wind from the southwest, alpine high temperature +1 C, freezing level 1600 m.
Avalanche Summary
Natural storm and wind slab avalanche activity up to size 1.5 was observed Friday and continued on Saturday, up to size 2. At least one of these was triggered by a natural cornice fall.
The previous storm yielded many large (size 2-3) storm slab avalanches both natural and explosive triggered, on Wednesday and Thursday.
We are sorry to report the news of 2 fatalities in the Montana Flathead region on Wednesday. The bed surface of the deadly avalanche was a crust formed and buried around Christmas. An illustrated photo can be found here. This crust has been observed widely in the Lizard Flathead region as well.
Snowpack Summary
15-25 cm of recent snow has been blown into wind slabs in the alpine by strong winds. Observed as high as 1800 m, a breakable crust sits on the surface from Friday's freezing rain event.
Below 1700 m, two noteworthy crusts exist: a thin lens crust from a freezing rain event sits 50 cm below the surface, and below that, a thick, hard melt-freeze crust formed by warm temperatures around Christmastime, occasionally found with surface hoar crystals ontop. As these crusts become buried deeper, they have the potential to turn into a persistent slab problem. We'll be keeping an eye on them going forward.Â
Hard snow in the mid snowpack sits above faceted snow and crusts near the bottom of the snowpack (100-170 cm deep). This weak lower snowpack has not been an active avalanche problem recently.
Terrain and Travel
- Be especially cautious as you transition into wind affected terrain.
- Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
Problems
Wind Slabs
Strong winds have formed formed wind loaded pockets in alpine lees such as below ridge crests and roll-overs.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 5th, 2020 5:00PM
