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Avalanche Forecast

Archived

Mar 31st, 2014–Apr 1st, 2014

Alpine
Natural avalanches possible, human triggered probable.
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

Olympics.

By Tuesday, the latest storm snow will be at least 2 days old and weaknesses in storm layers will have likely settled a great deal. Human triggering wind or storm slabs will be more difficult, but not impossible.  Watch for earlier wind slab deposits and also watch for solar effects on recent snow on steep exposed terrain.  

Detailed Forecast

A weak system should spread mainly increasing high clouds over the Olympics Tuesday with relatively light winds and moderate freezing levels.  This should cause partly cloudy weather in the Olympics Tuesday.

A mix of winter and spring snow conditions should persist Tuesday.  As storm slab and wind slab layers continue to settle and stabilize Tuesday, the main concern should begin to shift to wet loose avalanches on steep sun exposed terrain. This should be likely on solar slopes in all 3 elevations bands and will be possible on non-solar slopes. Watch for wet surface snow deeper than a few inches, roller balls in surface snow and small natural wet loose releases that usually precede more major wet loose snow avalanches. Avoid terrain traps where a small but powerful wet loose avalanche could have unintended consequences.

Continue to watch for areas of recent wind slab on lee slopes. This is likely on shaded north to east slopes near and above treeline. Watch for signs of cracking or firmer wind transported snow and approach open lee slopes with caution.

Remember to watch for cornices if you venture onto ridges Tuesday and avoid slopes below cornices. Cornice failures are often seen during the transition to spring weather.

Snowpack Discussion

A wintery weather pattern was renewed over the Northwest starting last Tuesday. About 2 feet of snow fell at Hurricane between last Tuesday and Sunday with less snow at lower elevations.

Avalanche conditions also became active through the weekend.  We are now seeing a mix of winter snow conditions mainly on shaded slopes at higher elevations and spring snow conditions on solar slopes and at lower elevations. 

A frontal system passing through on Friday brought moderate south winds and wet snowfall at Hurricane Ridge, with rain likely not far below in elevation. NWAC observer Katy Reid at Hurricane on Friday reported local wind slab along along lee ridges with pit tests giving stubborn but clean shears. She also found some storm snow instabilities giving clean results in hand tests at about 15 cm or 6" below the surface.

By Sunday, additional new snow at slightly colder temperatures was creating additional storm and wind slab concerns, especially with the effects of strong solar input at times.

Little new snow has fallen since Sunday and this is allowing storm weaknesses to quickly settle and stabilize. While we are in a stabilizing pattern, do not let your guard down.  While human triggering may have become more difficult, it only takes being in the wrong place.  Continue to choose conservative terrain, watching for previous wind deposits.     

Wind slab cracking from ski at Hurricane Ridge, Near Tree Line, Sunday 3/30 by NWAC observer Katy Reid.

Natural wind slab avalanches likely from Saturday were found at Hurricane by Katy on Sunday with several releases up to size 2 mainly 6-12 inches but stepping up to 2.5 feet on a north slope. Tests indicated a clean interface at about 20 cm in the storm snow.

Natural wind slab avalanches found at Hurricane on Sunday by NWAC observer Katy Reid.

Problems

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.

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.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.