Ahead of the new snow forecast for Sunday (1/22), we have been mapping out the
general surface conditions to help predict how well any new snow will bond, as
well as existing snow that is available for transport with higher winds.
The surface snow on Turnagain Pass has a variety of faceted grains. Most areas
have around 2-10″ of loose snow over a wind slab of varying depth. The loose
snow is made up of decomposing precipitation particles that fell on 1/12 (10
days ago) that have been turning to small grained facets with our cold and clear
weather.
Surface hoar is most prominent in valley bottoms (1-3cm), around treeline it is
2-3mm and decreasing to 1mm or non-existent above treeline. It is sitting on
soft snow in most places which limits its concern for being a future weak layer.
Bottom line – there is a lot of loose faceted snow out there to act as a weak
layer if overloaded by a significant load. Additionally, this snow is sitting on
a hard winded layer in many areas that can provide a great bed surface for sliding.
Near suface facets, 3cm depth, forming in the decomposing new snow from 10 days ago (1/12) - 1mm grid
Pit from 3200' SW facing, 38 deg slope
Precipitation particle from (1/12) persisting close to it's original form just under a 5cm wind slab and 25cm deep - 1mm grid
Larger grained mixed formes deeper in pack (70-80cm deep) - 1mm grid
Surface hoar at 2500' (2-3mm) - on a 3mm grid