Avalanche Forecast
Issued: Mar 3rd, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
ahanna,
Avalanche Canada
It's spicy out there right now. Between fresh wind slabs and a touchy persistent weak layer, human triggered avalanches are likely. Keep in mind it's not always the first rider who triggers the slab.
Summary
Confidence
Moderate - Forecast snowfall amounts are uncertain. Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather.
Weather Forecast
Tuesday night: 5-20 cm new snow. Strong west wind. Freezing level 1200 m.
Wednesday: 5-10 cm new snow. Moderate northwest wind. Freezing level 1200 m.
Thursday: Flurries. Moderate southwest wind, strong at ridgetop. Freezing level 1700 m.
Friday: 5-20 cm new snow. Light southwest wind. Freezing level 1500 m.
Avalanche Summary
Since the weekend we have seen a surge in persistent slab avalanche activity on the February 22 surface hoar layer. Numerous skier triggered and remote triggered size 1-2 have been reported by nearly every ski operation region wide even as professionals tiptoe around, avoiding suspect terrain features. Observations are from all aspects and elevations, but especially concentrated on north to east aspects around treeline.
In several instances, slopes were ski cut with no results, only to have the third or fourth skier in the group accidentally trigger the slab. In other cases, avalanches were triggered on slopes with old ski tracks or where avalanches had already released.
Naturals triggered by cornice falls, loose snow running out of extreme terrain or warming temperatures were observed mostly around size 2, but up to size 3. Natural wind slab avalanches size 1-2.5 were observed on easterly aspects in the alpine on Sunday.
Snowpack Summary
New storm slabs are forming in snowier areas of the region, with 25 cm falling in some areas by end of the day Wednesday with light to moderate westerly wind.
A weak layer of widespread surface hoar sits 40-70 cm deep, ontop of a crust on solar aspects. The overlying snow has been cohered into slabs by incremental loading through successive storms, wind and mild temperatures. As slab character and depth increase, so do reactivity and size of avalanches failing on the weak layer. Read more about surface hoar on our forecaster blog!
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Surface hoar distribution is highly variable. Avoid generalizing your observations.
- In times of uncertainty conservative terrain choices are our best defense.
- Even brief periods of direct sun could produce natural avalanches.
Problems
Wind Slabs
Light snowfall and strong winds are building fresh wind slabs in the alpine and open areas at treeline. If triggered, windslabs have the potential to trigger deeper weak layers.
Aspects: North, North East, East, South East.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer of surface hoar sits 40-70 cm deep. Read more about surface hoar on our forecaster blog! Human triggering of this layer is very likely, and has been observed extensively through the region over the last few days even as professionals seek to actively avoid suspect terrain features (eg. convex rolls). Observations are from all aspects and elevations, but especially concentrated on north to east aspects around treeline.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 4th, 2020 5:00PM
