Avalanche Forecast
Issued: Mar 4th, 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
Navigate around wind loaded terrain and avoid big slopes getting hit by the sun.
Summary
Confidence
Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack. Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.
Weather Forecast
Dry sunny weather until a storm hits the region on Friday and Saturday.
WEDNESDAY NIGHT: Clear skies, light to moderate west wind, freezing level drops to valley bottom with alpine temperatures dropping to -10 C.
THURSDAY: Sunny, freezing level climbing from valley bottom to 1800 m in the afternoon, moderate to strong southwest wind, alpine high temperatures around -1 C.
FRIDAY: Increasing cloud with light flurries in the afternoon bringing up to 5 cm of new snow, freezing level around 1500 m, moderate wind from the southwest, alpine high temperatures around -3 C.
SATURDAY: Stormy weather with 10-25 cm of new snow, moderate wind from various directions, freezing level at valley bottom with alpine high temperatures around -8 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
A storm passing through the region on Tuesday night delivered 5-10 cm to the region with closer to 15-20 cm along the northern parts of the region near Kananaskis Country. This snow was accompanied with strong to extreme wind from the west and formed fresh wind slabs in exposed terrain. A crust can be found near the surface up to 2300 m on solar aspects and up to 1700 m on all other aspects, however, but midday Thursday warm sunny weather could melt the surface on these slopes.
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
- Choose gentle slopes without steep terrain above.
- Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
- Avoid exposure to overhead hazards when solar radiation is strong.
- Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
Problems
Wind Slabs
Recent snow has been blown around by strong to extreme wind from the west over the past few days. Watch for wind slabs in the immediate lee of ridges. Warm sunny weather on Thursday could weaken these slabs and make them more reactive.
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, and will continue to be a concern on big terrain features. Evidence of deep persistent slab avalanches has been focused in the Sparwood-Elkford area over the past month.
Human triggering is most likely around steep rocky terrain features, or anywhere the snowpack is thin and weak. Natural triggering is possible on slopes below cornices and on slopes that warm up in the heat of the day.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 5th, 2020 4:00PM
