Another storm, another rapid uptick in avalanche danger. Enjoy another powder day in lower angled, low consequence terrain while the snowpack adjusts.
Another storm pulse will quickly form unstable storm slabs, especially where where wind-loaded. Rising freezing levels and rain will promote natural avalanches in the afternoon.
Rising freezing levels could bring rain to as high as treeline on Saturday. Where new snow becomes moist or wet, loose wet avalanches may be triggered naturally or with rider traffic.
Explosives control in the Mount Washington area produced several more size 1.5 - 2 wind slabs in west-facing terrain on Thursday.
Numerous size 1 - 1.5 slabs were observed throughout north-facing terrain in the same area Wednesday as well as a size 2 storm slab triggered accidentally by a skier walking along a ridgeline. It occurred on a northwest-facing 30-degree slope at treeline, fractured 100 m wide, ran 50 m, and featured a 40 cm crown.
A wide-ranging 15 - 50 cm of new snow should accumulate by end of day Saturday. This adds to 40 - 60 cm of new snow from the Christmas storm. Accumulations in the west coast alpine may be significantly higher. Strong winds elsewhere have led to up to 200 cm sitting on the pre-storm crust!
Fluctuating freezing levels formed at least two mid-storm failure planes in the new snow, both of which produced moderate, sudden snowpack test results on Thursday. These weaknesses are expected to stabilize relatively quickly.
Below the new snow, the snowpack is thoroughly settled and bonded.
Snowpack depths at treeline are now about 130 -180 cm on the north and south island, closer to 250 to 300 cm on the central island.
Friday Night
Cloudy with increasing snowfall bringing 10 to 30 cm of new snow, greatest in the west. 40 to 50 km/h southeast ridgetop wind. Freezing level 900 - 1100 m.
Saturday
Cloudy with continuing, increasingly wet flurries bringing 5 to 25 cm of new snow, greatest in the west. 50 to 60 km/h southwest ridgetop wind. Freezing level 1300 - 1400 m.
Sunday
Cloudy with scattered flurries bringing up to 5 cm of new snow. 30 to 40 km/h southeast ridgetop wind shifting southwest. Freezing level 1000 m.
Monday
Mainly cloudy with isolated flurries. 30 to 40 km/h southwest ridgetop wind. Freezing level 1100 m.
More details can be found in the Mountain Weather Forecast.
