Use caution on north facing slopes in the alpine: riders are triggering a reactive wind slab.
Its spring and conditions vary greatly depending on aspect, elevation and time of day.
Strong winds have formed wind slabs on lee slopes at treeline and in the alpine. In isolated pockets on high north aspects, surface hoar is present below the slab. We have limited observations of this interface. In some locations the slab of snow is moist and running on a crust.
Intense spring sun will trigger wet loose avalanches in a weak snowpack below treeline. Rider triggering is also possible, use caution in steep terrain and around terrain traps.
Backcountry report of skier triggered, sz 2 wind slab on the Dome glacier @ 2450 m on a NE asp. This avalanche likely failed on an isolated layer of surface down 10-30 cm. See MIN on Thursday for another skier accidental, sz 2.5 with involvement on this interface. Dig down and have a look for this layer before jumping into large or committing features.
Thursday our field team found a reactive storm slab on a steep alpine features, that failed 10-20cm deep and 5m wide.
Falling freezing levels will strength upper snowpack, freezing a series of melt-freeze crusts. Seek high alpine, north facing slopes to find dry snow. Recent storm snow has formed a slab on lee features, with a recent crust as a bed surface. This wind slab is most reactive on lee slopes loaded by southerly winds and where spotty surface exists.
Use caution below treeline, conditions are variable and challenging travel exists.
Unstable, moist spring weather continues, with falling freezing levels and light snow on Saturday.
Tonight Cloudy w/clear periods Alp low -7°C. Ridge wind light SW. Freezing Level (FZL) 1200m.
Sat Sun, cloud, and flurries. Alp high -6°C. Ridge wind W 25-40km/h. FZL 1600m.
Sun Mix sun & cloud. Ridge wind W 15-30. FZL 1800m.
Mon Clouds with sun, isolated flurries. Alp high -4°C. Ridge wind W 15-30. FZL 1800m
