Avalanche Forecast
Issued: Feb 22nd, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
mconlan,
Avalanche Canada
Recently formed storm and wind slabs will likely remain triggerable to riders on Tuesday, as will be the lurking weak layer that has caught many riders in the past few weeks. Conservative terrain travel is recommended!
Summary
Confidence
Moderate - Uncertainty is due to the track & intensity of the incoming weather system.
Weather Forecast
MONDAY NIGHT: Cloudy with snowfall then clearing, accumulation 10 to 20 cm, 60 km/h west wind, alpine temperature -7 C, freezing level dropping to valley bottom overnight.
TUESDAY: Mix of sun and cloud, 30 km/h west wind, alpine temperature -9 C.
WEDNESDAY: Clear skies, 20 km/h southwest wind, alpine temperature -9 C.
THURSDAY: Cloudy with snowfall, accumulation 5 to 10 cm, 30 km/h southwest wind, alpine temperature -10 C.
Avalanche Summary
Much of the area wasn't visible on Sunday and Monday due to stormy conditions, but many large (size 2) storm slabs were triggered on Monday near Fernie. Extensive natural and human-triggered avalanches were probable across the region during the stormy period. We may see further evidence of the activity as the skies clear on Tuesday.
Snowpack Summary
Around 20 to 50 cm of snow fell on Monday, with the most in the east of the region near the divide. Storm slabs likely developed rapidly. The freezing level hovered around 1600 m, soaking the snowpack below. Strong south to southwest wind dominated, forming new wind slabs in exposed terrain. More snow, strong west wind, and a dropping freezing level are forecast for Monday night, building on these slabs into Tuesday.
All this snow and rain are loading a weak layer found around 50 to 100 cm deep. The layer may consist of weak and feathery surface hoar, sugary faceted grains, or faceted grains associated with a hard melt-freeze crust. Many avalanches in the past few weeks have been triggered on these layers.
There are presently no deeper concerns.
Terrain and Travel
- Choose conservative terrain and watch for clues of instability.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
- The trees are not the safe-haven they normally are at this time. Terrain at treeline is primed for human triggered avalanches.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Problems
Storm Slabs
Both storm and wind slabs remain likely to be triggered by riders on Tuesday. The slabs may be around 20 to 50 cm thick, depending on how much snow fell in your riding area. Conservative terrain travel is recommended until the snow has some time to bond to the snowpack.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Loads of large avalanches have been triggered on this layer of surface hoar, faceted grains, and/or a melt-freeze crust, now found around 50 to 100 cm deep. The layer has been most problematic around treeline elevations and in openings below treeline, but also reaches into the lower alpine. Avalanches have occurred on surprisingly shallow slope angles and they can easily be remotely triggered.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 23rd, 2021 4:00PM
