Strong wind and recent snow have formed reactive wind slabs.
Warm temperatures, weak cornices combined with a lingering deep persistent slab problem may equal large and destructive avalanches. Its a good time to approach the mountains cautiously and even expect surprises.
Up to 20 cm of snow accompanied by strong winds and warmer temperatures have formed reactive wind slabs. They will likely be touchier on leeward slopes with deeper, wind-loaded conditions, especially where they sit on surface hoar or crusts.
Natural cornice fall is possible with upper elevation warming and solar radiation. Cornice fall could be a hazard on its own and it could trigger a deeper slab avalanche from the slope below.
Loose wet avalanches are possible, especially on southerly aspects and steeper slopes.
The early December crust can be found 140-200 cm deep. A deep persistent slab problem could wake up with forecast warming, solar radiation, cornice fall, and step-downs from smaller avalanches.
A ridge of high pressure brings warming and sunny skies through the weekend. Alpine inversions may see temperatures as high as +5 degrees with some valley bottoms possibly seeing cloud and cooler air pooling at lower elevations.
Saturday/ Sunday: Mix of sun and cloud. Freezing levels rise through the day 2000-2500 m with generally clear skies. Alpine temperatures near +5 C. Possible inversion may hold valley cloud and cooler temperatures down low. Ridgetop winds moderate from the northwest. Expect cooling overnight.
Monday: Mix of sun and cloud and strong ridgetop wind from the northwest. Alpine temperatures -3 and freezing levels forecast to drop to 1200 m.
No new reports by 4pm on Friday.
On Thursday, numerous storm slab avalanches were reported up to size 2.
Reactive wind slabs may be found on Saturday. But most concerning is the warm weather this weekend. Warming, solar radiation, smaller surface avalanches, and cornice fall could trigger deep persistent slabs. This layer has been dormant but to no surprise could wake up.
During the warm previous storm, mid-last week, a large widespread avalanche cycle occurred with most avalanches releasing within the storm snow and some on Jan 11 surface hoar layer. Strong solar radiation and warm temperatures were also at play after the storm, producing numerous avalanches at all elevations and scouring avalanche paths to the ground in places.
10-20 cm of recent snow combined with strong winds has formed reactive wind slabs and bury a series of recent surface hoar layers and melt-freeze crusts found down 15 cm and another down 25 cm. These extend to 2400 m and are most prevalent (thicker) on southerly aspects.
Digging deeper, down 50-60 cm is yet another surface hoar layer that has seen recent avalanche activity. A well-consolidated mid-pack exists below this and above the early December crust/facet interface.
The early December crust/facet layer has been responsible for sporadic but very large, persistent slab avalanches over the past month. The crust is now buried 120-200 cm deep except in thin, wind-affected areas near ridgetops. Warming, cornice fall, and smaller avalanches through the forecast period may be enough to wake this layer up and initiate large to very large avalanches.
