PNW Snowpack Analysis

SNOWPACK ANALYSIS
The most recent storm occurred Monday. This storm began
warm with rain or freezing rain in many areas early
Monday and cooled dramatically later Monday and was
accompanied by very strong west to northwest crest level
winds. This produced a crust to about 4 to 5000 feet in
the north and to above 7000 feet in the south with
varying amounts of new snow above. The new snow that
accumulated by Tuesday morning ranged from about 6 to 15
inches with the greatest snow received in the Stevens to
Snoqualmie Pass areas in convergence. Previous mild
weather and sunshine last weekend along with the rain or
freezing rain early Monday helped to settle and
consolidate the deep northwest snowpack while forming an
underlying crust in all areas except the higher
elevations in the north and east slopes.

The recent sunny mild weather last weekend and recently
formed near surface crust has now shifted the danger away
from some of the old deeply buried weak layers to mainly
isolated surface wind slab layers produced late Monday
and Monday night. These should be near ridges and mainly
above about 5000 feet and most prevalent on northeast to
southeast facing slopes near ridges and at higher
elevations.

Elsewhere, some good and relatively stable snow
conditions exist on sun and wind sheltered slopes,
consisting of low density surface snow and gradually
increasing density snow with depth.

A field trip Wednesday by NWAC colleague and myself into
the Stevens Pass BC near Skyline ridge showed mostly
unconsolidated and stable surface snow of 14 to 18 inches
over a strong crust and some excellent conditions. Wind
affects from Monday were evident along an east facing
ridge at about 5400 feet where two small isolated soft
slabs were triggered near the ridge by other parties.
These were isolated in nature and slid on the recent
crust. Similar snow conditions were reported in the
Snoqualmie Pass area Tuesday ranging from 3000 to 5000
feet.