Avalanche Forecast
Issued: Mar 7th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
lbaker,
Avalanche Canada
The sun packs a punch this time of year, even brief periods of strong solar input could increase the reactivity of wind slabs. Reduce your exposure to avalanche terrain and overhead hazard during sunny periods.
Summary
Confidence
Avalanche Summary
On Sunday and Monday, several natural wind slab avalanches were observed to size 2.5 on westerly aspects between 1800 and 1400 m. These avalanches may have been triggered by cornice fall or strong easterly winds on Saturday night. A skier accidental, size 1.5, wind slab avalanche was reported on a northeast aspect at 1900 m. Check out this MIN from Saturday showcasing the current wind slab problem.
Last week, several skier triggered persistent slab avalanches, up to size 2.5, were reported in the Norns and Rossland region. Many of these avalanches failed on weak layers from February and January and occurred at treeline. Though activity has tapered off on this layer it could still be reactive to large triggers.
Snowpack Summary
40-60 cm of storm snow has been redistributed by shifting winds into wind slabs on all aspects at treeline and above. This storm snow sits over a wind affected layer at all elevations. On open solar aspects, a melt-freeze crust covers the surface.
A layer of surface hoar can be found on shaded slopes, and a sun crust on sun affected slopes buried 40 to 70 cm deep. Another layer from January is buried up to 50 cm below this.
The lower snowpack includes a layer of weak sugary crystals near the ground. These facets are slowly gaining strength and have not produced recent avalanche activity. We continue to track the layer and watch for any signs that it could wake up and produce very large avalanches.
Weather Summary
Tuesday Night
Clear skies. Southeasterly winds 15-25 km/h. Treeline temperatures, low of -9. Freezing levels drop to valley bottom.
Wednesday
Mainly sunny with a few clouds. Easterly winds 15-25 km/h. Treeline temperatures, high of -6. Freezing levels hover around 1300 m.
Thursday
A mix of sun and cloud. Southeasterly winds 10-25 km/h. Treeline temperatures, high of -7. Freezing levels 1000 m.
Friday
Cloudy and scattered flurries, 4-6 cm accumulation. Southeast winds 25-40 km/h. Treeline temperatures, high of -7. Freezing levels remain at valley bottom.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Minimize exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- Surface hoar distribution is highly variable. Avoid generalizing your observations.
Problems
Wind Slabs
Variable winds over the past few days mean that wind slabs can be found on all aspects. Most recently natural wind slab avalanche activity has been reported on westerly aspects. Periods of strong winds on the weekend may have formed wind slabs further down the slope than usual.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
There are two layers of concern in the upper and mid pack. These layers are generally made up of facets and surface hoar but on south aspects a crust can be found. These layers are most likely to be triggered on sparsely treed slopes at treeline and below. These layers were reactive to skier triggering in the Norns and Rossland region last week.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Mar 8th, 2023 4:00PM
