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 Deep Persistent Slabs.
shorton,
Avalanche Canada
The lingering deep persistent slab avalanche problem makes it impossible to have 100% confidence, especially in bigger alpine terrain features.
Summary
Confidence
Weather Forecast
TUESDAY NIGHT: A cold front crossing the region delivers 5-15 cm of snow, strong to extreme wind from the west, freezing level drops to valley bottom with alpine temperatures dropping to -8 C.
WEDNESDAY: Cloudy in the morning then some sunny breaks in the afternoon, strong northwest wind, alpine temperatures around -6 C.
THURSDAY: Sunny, freezing level climbing from valley bottom to 1800 m in the afternoon, moderate southwest wind, alpine temperatures around -1 C.
FRIDAY: Increasing cloud with light flurries in the afternoon, moderate wind from the southwest, freezing level steady around 1600 m, alpine high temperatures around -3 C.
Avalanche Summary
No avalanches have been reported since last week, but there have been limited field observations. A few natural size 2 wind slabs have been reported on north and east aspects in the neighbouring Kananaskis region.
A very large (size 3) deep persistent slab avalanche was observed north of Sparwood last Friday on a steep southeast facing alpine slope. This follows a pattern of sporadic deep slab releases in the upper Elk Valley including this natural avalanche from Feb 11 and this sled triggered avalanche from Feb 9. These types of large avalanches will be most likely during periods of heavy loading or intense warming.
Snowpack Summary
Strong to extreme wind has hammered open terrain, scouring some slopes and forming wind slabs on other slopes. A crust can be found near the surface up to 2300 m on solar aspects and up to 1700 m on all other aspects.
A thick rain crust sits 40-80 cm below the surface and can be found up to 2100 m. Avalanche activity was last observed at the faceting interface between this crust and overlying snow on February 17. The mid-pack is well settled and strong, but the base of the snowpack contains basal facets that are most prominent in shallow rocky start zones.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
Problems
Wind Slabs
Watch for thin wind slabs forming in the immediate lee of ridges. Also be aware of the potential for cornice failures, large cornices overhang many ridge lines.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
Weak snow at the bottom of the snowpack hasn't gone away unfortunately. Cornice failures could be the perfect trigger for a deep persistent slab. Human triggering would be most likely around steep rocky terrain features, or anywhere the snowpack is thin and weak. Evidence of deep persistent slab avalanche activity over the past month has been focused in the Sparwood-Elkford area.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 4th, 2020 4:00PM
