Take a step back to more mellow terrain, conditions are changing for Friday.The wind once again has a source of snow from which to form fresh, reactive wind slabs.
Fresh snow and moderate to strong southerly winds are likely forming reactive new wind slabs through the day. Watch for visible wind transport, and signs of instability like shooting cracks.
On Wednesday, a large (size 2) avalanche was reported on a north aspect in the alpine. It may have failed on a layer of weak, feathery surface hoar crystals that have been preserved in very isolated areas. See photo below. Field observations have been limited, if you're out in the backcountry please consider submitting your observations to the Mountain Information Network.
10 to 20 cm of new snow covers old, firm, wind-affected or wind-scoured surfaces. See photo below for a picture of terrain prior to the storm. You may find a sun crust on the surface at treeline and below on steep, south aspects. Moderate to strong winds will likely form deeper deposits of fresh, reactive wind slab that may not stick well to the old surface.
Below 1500 m, a thick melt-freeze crust is buried 50 to 100 cm deep. In Haines Pass this crust was not found at 1400 m, but we expect that it does exist at lower elevations.
The midpack is generally strong and bridges the weak crystals at the base of the snowpack.
The average snowpack depth at treeline is around 200 cm, as deep as 300 cm in Haines Pass.
Thursday Night
Mostly cloudy. 2 to 5 cm of snow expected. Moderate southeast ridgetop wind. Treeline low around -10 °C.
Friday
Mostly cloudy. 5 to 10 cm of snow expected in White Pass, and 15 to 20 cm in Haines/Chilkat Pass. Moderate to strong south ridgetop wind. Treeline high around -7 °C.
Saturday
Mostly cloudy. 10-20 cm of snow expected in White Pass and Haines/Chilkat Pass. Moderate to strong southwest ridgetop wind. Treeline temperature around -5 °C.
Sunday
Mostly cloudy. 5-10 cm of snow expected in White Pass and Haines/Chilkat Pass. Moderate south ridgetop wind. Treeline temperature around -8 °C.
More details can be found in the Mountain Weather Forecast.
