Avalanche Forecast
Issued: Feb 29th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
cmortenson,
Avalanche Canada
Limit exposure to large avalanches by sticking to simple terrain. A buried Surface Hoar layer lurks and is showing signs of touchy human triggered avalanches with recent snow, especially where snow is wind affected. Check out this Fx blog on Surface Hoar.
Summary
Confidence
Weather Forecast
SATURDAY NIGHT: Cloudy with clear periods. Winds light to moderate North. Alpine low temperature -15 C with freezing levels at valley bottom.
SUNDAY: A mix of sun and cloud with scattered flurries, accumulations Trace to 5cm. Winds moderate Southwest. Alpine high temperatures near -9 C and freezing levels 600m.
MONDAY: Mainly cloudy with sunny periods and isolated flurries, accumulations Trace to 10cm. Winds moderate West gusting strong. Alpine temperatures high of -6 and lows -10 C with freezing levels near 1200m.
Tuesday: Mainly cloudy with snow flurries, accumulation 5-15cm. Winds moderate to strong West gusting extreme. Alpine temperatures high of -6 and lows -10 C with freezing levels near 1200m
Avalanche Summary
Early reports from Saturday include numerous easily triggered large (size 2) human triggered avalanche on Surface Hoar down 50-70cm at treeline.
On Friday there were numerous reports of small (Size 1) skier triggered avalanches on Surface Hoar down 40-50cm from 1400-2100m on all aspects.
Check out this MIN for a report of how the high freezing levels on Friday impacted low and mid elevation
Snowpack Summary
10-25cm of snow fell across the region Friday into Saturday with more snow reported in the North and adjacent to highest of mountains. Winds were moderate to strong from the Southwest as new snow fell. This new snow likely formed widespread wind affect and wind slab in Alpine and exposed treeline locations, particularly near ridges.
40-70 cm or recent snow now overlays the widespread Surface Hoar (size 5 to 15 mm) that was found at all elevations and on all aspects. Recent warm temperatures have built slab like properties in this recent snow, particularly at mid and low elevations.
There is variability in the reactivity and distribution of this layer, particularly in the northern half of the region. In the southern half, this layer exists on all aspects and elevations except for steep, sun-exposed aspects where it was melted by sun and formed a melt-freeze crust. So far, the overlying snow has been reactive to human activity where the wind has redistributed it, forming a slab. This has been most common around treeline and alpine elevations in the south of the region.
The mid and lower snowpack is generally well-settled and strong.
Terrain and Travel
- Stick to simple terrain or small features with limited consequence.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- 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.
Problems
Persistent Slabs
Additional new snow continues to load a widespread layer of surface hoar, with about 30 to 70 cm overlying it now. This layer appears to be reaching "threshold" where human triggering is likely. Watch for signs of instability such as shooting cracks and whumphing. So far, the layer has been most reactive at treeline and alpine elevations, where the recent snow has been redistributed by the wind and formed a slab above the surface hoar.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Strong southwest wind has formed wind slabs in exposed terrain. Use added caution in lee terrain features, particularly near ridges.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 1st, 2020 5:00PM
