Avalanche Forecast
Issued: Feb 24th, 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
Danger will increase as the day progresses with new snowfall and strong wind. Continue to travel diligently, as the buried weak layer is still surprising riders.
Summary
Confidence
Moderate - Uncertainty is due to the track & intensity of the incoming weather system.
Weather Forecast
WEDNESDAY NIGHT: Increasing clouds, 30 to 50 km/h southwest wind, alpine temperature -10 C.
THURSDAY: Cloudy with snowfall, accumulation 10 to 20 cm, 30 to 50 km/h southwest wind, alpine temperature -10 C.
FRIDAY: Cloudy with snowfall, accumulation 5 to 10 cm, 30 km/h west wind, alpine temperature -9 C.
SATURDAY: Clear skies, 30 km/h northwest wind, alpine temperature -10 C.
Avalanche Summary
Many large (size 2 to 2.5) storm and wind slab avalanches were triggered naturally, by skiers, and using explosives on Monday and Tuesday. The slabs were generally 30 to 50 cm thick, most often at treeline and alpine elevations, and occurred on all aspects but many of them on north to east aspects.
Looking towards Thursday, riders are still capable of triggering storm slabs, wind slabs in wind-loaded terrain, and persistent slabs. Conditions are not easily managed right now, warranting a conservative mindset!
Snowpack Summary
Stormy conditions enter the region on Thursday, bringing new snow and strong wind. Storm slabs are expected to build in sheltered areas at all elevations and on all aspects. Wind slabs are expected to build over the day in exposed terrain at treeline and alpine elevations in lee terrain features. These slabs will build on top of storm slabs formed early this week that still may be triggerable by riders, particularly where they overly sugary faceted snow from mid-February's cold drought.
A weak layer found around 50 to 80 cm deep that was buried late-January has been prevalent in the region during February. 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 this layer by riders and naturally.
There are presently no deeper concerns.
Terrain and Travel
- Watch for changing conditions today, storm slabs may become increasingly reactive.
- The trees are not the safe-haven they normally are at this time. Terrain at treeline is primed for human triggered avalanches.
- Choose conservative terrain and watch for clues of instability.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Problems
Storm Slabs
New storm and wind slabs are expected to form over the day on Thursday as the next storm rolls through, so expect the danger to increase as the day progresses. Storm slabs formed earlier this week also remain likely to be triggered by riders. The slabs may be around 20 to 50 cm thick, depending on how much snow fell in your riding area, and they may overly sugar faceted grains. 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
Many large avalanches have been triggered on this layer of surface hoar, faceted grains, and/or a melt-freeze crust, found around 50 to 80 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 the layer can easily be remotely triggered.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 25th, 2021 4:00PM
