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RegisterJan 15th, 2015–Jan 16th, 2015
Stevens Pass.
New storm and wind slab mainly on lee aspects may bond poorly to the existing snow surface, especially near and above treeline where smooth. Watch for unstable slab layers and avoid steep lee slopes that may have received wind transported recent snow, especially steep NW thru NE facing slopes.
A period of moderate to briefly heavy precipitation expected overnight should build storm slab layers, especially near treeline and above.
New storm and wind slab should be likely Friday, especially near and above treeline. Strong winds overnight Thursday will have likely built unstable slab layers on NW-NE facing slopes, mainly below ridges.
Light and decreasing snow showers are expected through the day Friday with a cooling trend. This should allow for slowly improving avalanche conditions as storm layers begin to settle.
On backcountry travel safety note, watch for terrain hazards (exposed rocks, trees, streams, etc.) at lower elevations and on wind scoured aspects.
An approaching storm will move across the area Thursday night, changing the recent Snowscape significantly, from one dominated by crust layers. The last storm arrived on January 4th, depositing about 5-15 inches of snowfall, followed by warming and heavy rain on the 5th. This caused a widespread avalanche cycle, followed by the recent stretch of high pressure.
You can see some great images of the aftermath of the January 5th slide cycles taken Wednesday by NWAC observer Jeremy Allyn above Paradise, Mt Rainier,.
The latest high pressure has been marked by warm temperatures and sunshine in most alpine zones with cooler and sometimes foggy conditions in the valleys and Cascade Passes.
The snowpack in most areas consists of strong surface melt-freeze crusts of varying thicknesses formed over stabilized rounded grain layers. Surface crusts have been recently reported to be fairly rough, which may decrease the ease of triggering new slabs. There have also been some reports of existing surface hoar which has formed in generally narrow elevation bands in the treeline to near treeline band, associated mainly with valley fog or recent easterly winds in the passes. Some windward or southerly aspects have little if any snow cover so terrain anchoring will help there.
With the overall strength of the snowpack, any newly developing storm slab avalanches should be limited to new snow.