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Avalanche Forecast

Archived

Jan 14th, 2014–Jan 15th, 2014

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Snoqualmie Pass.

The avalanche danger should continue to slowly diminish Wednesday for previous storm layers.  However, warming and sunshine Wednesday should increase wet snow and possible wet avalanches on steep southerly facing terrain. 

Detailed Forecast

Mostly sunny weather, mild temperatures and light to moderate crest level winds are expected Wednesday.  This weather should allow for earlier formed weak layers to continue to settle and stabilize as well as earlier formed wind and storm slabs.  This weather will also help to consolidate the large recent storm snow deposits and lead to a slowly stabilizing snowpack.  

However warming and sunshine may lead to wet snow conditions and possible loose-wet slides on steeper solar aspects.  

At elevations above treeline, earlier formed wind slab should be somewhat slower to stabilize so evaluate snow and terrain carefully and identify features of concern, such as lee slopes below ridges, cornice features, or steep break overs on slopes.  These earlier formed wind slabs near ridges in the alpine region should remain the greatest concern, most probably on north through southeast facing slopes.  

Snowpack Discussion

A nearly week long storm cycle began last Tuesday and finished with a whimper Tuesday morning.  Skies have begun clearing Tuesday and temperatures rising once again under a return to high pressure. This major storm cycle delivered some hefty water and snow amounts while freezing levels/snow levels fluctuated widely with systems.  Five day storm snow amounts ending Monday ranged on average from 60-150 cm both, with the lesser quantities confined to lower elevations and Cascade passes where more rain occurred.  Most mid and higher elevation areas received 1-2 m of storm snow.  

This active storm cycle produced several avalanche releases both natural and triggered over the past few days.  Freezing levels fluctuated significantly and there were also periods of very very strong winds.  This weather caused several significant storm layers of weaker low density snow deposited during cooler temperatures contrasted with wet snow or crust layers or dense wind affected snow layers. 

Most recent avalanche activity either, natural, ski or explosive triggered has remained within storm snow layers, ranging from 15-60 cm. However, some slides released on a buried weak lower density layer above an earlier formed crust layer down some 60-120 cm or more depending upon locale.  Field observations this Sunday near Stevens Pass on a lee slope just above 5000 ft showed wind loaded storm snow of 1.2 m.    

Recent avalanche activity: There were several reported soft slab releases Friday in the Mt Baker backcountry, felt to be releasing on a weaker lower density storm snow layer above a previous crust layer. However the snowpack has significantly changed with recent additional loading, warming as well as significant overall settlement helping move towards slow stabilization.  There were numerous new natural and triggered slides near Mt Baker on Shuksan arm and vicinity Sunday with slides on Shuksan estimated with Destructive potential 3 (destroy a wood frame house!).  Another natural release was reported early Sunday afternoon that likely released late morning during warming and heavy loading east of Stevens Pass.  The slide path is known as West Camp of Rock Mountain and was rated as D3/R2 N-SS, with a start zone about 5900 ft but poor visibility limited viewing.  

An NWAC observer in the Stevens Pass area Sunday reported sensitive storm slab with shooting cracks below treeline and good wind transport on higher N thru SE slopes.

Warming and additional rain Monday and Monday night at mid and lower elevations in the passes allowed for a saturated wet surface snow layer of nearly 1 meter as reported in the Stevens Pass area Tuesday. The saturated wet surface snow coupled with sunshine and warming produced a wet snow avalanche cycle witnessed by NWAC observer Dallas Glass just east of Stevens Pass Tuesday afternoon.   photo below.

 

One of numerous natural wet slides releasing from 1200-1400 Tuesday 1-14 just east of Stevens Pass.  Starting zones: rocky outcrops ~40 deg, S-SE aspects from ~4700-4900' - size D2 with some breaking trees. (Photo by Dallas Glass)

For the west slopes of the Cascades and Olympics, a generally favorable mid and lower snowpack exists, even if well below seasonal norms, consisting of various crust layers, rounded grains, and melt-freeze crystals.  

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.