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Avalanche Forecast

Archived

Mar 26th, 2018–Mar 27th, 2018

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.

Regions

Olympics.

Rising snow levels on Tuesday will produce small Loose Wet avalanches near and below treeline. Watch for warning signs like new roller balls, pinwheels, and natural Loose Wet avalanches as temperatures rise and light snow turns to rain near and below treeline. Shallow new Wind Slabs will form mainly above treeline Tuesday as increasing winds transport new and recent snowfall onto lee slopes at higher elevations.

Detailed Forecast

Rising snow levels on Tuesday will produce small Loose Wet avalanches near and below treeline. Watch for warning signs like new roller balls, pinwheels, and natural Loose Wet avalanches as temperatures rise and light snow turns to rain near and below treeline. Even small Loose Wet avalanches may carry you into terrain with high consequences such as over cliffs or into gullies. Avoid slopes where loose wet avalanches may become large by entraining deeper amounts of recent snowfall.

Shallow new Wind Slabs will form mainly above treeline Tuesday as increasing winds transport new and recent snowfall onto lee slopes at higher elevations. You may be able to trigger a Wind Slab avalanche at upper elevations on steep slopes near ridge tops or in cross-loaded terrain features. Watch for clues like variable snow height, drifts, cornices, and stiff snow that produces cracking. These are all indicators that you could trigger a Wind Slab. You can avoid triggering these avalanches by steering around steep roll-overs, unsupported features, and obvious start zones where you suspect Wind Slabs.

Snowpack Discussion

Cloudy skies, intermittent snowfall and slowly rising snow levels summed up the weather at Hurricane Ridge Monday. Several inches of snowpack settlement have occurred since the last snowfall. 

A skier triggered a Wind Slab avalanche late in the day Friday or early Saturday morning. These Wind Slabs were formed by moderate to strong southerly winds redistributing 10" of new snow that fell Thursday through Friday. Wind slabs were found on northerly aspects near and above treeline and stripped snow off of exposed southerly aspects.

Weaker layers of sugary facets and thin crusts have been found within the snowpack. Current observations suggest that these weak layers are not widespread. You are most likely to find older weak snow on East facing slopes about 1 ft (30cm) below the snow surface.

There are no other significant layers of concern in the snowpack at this time.

Observations

On Saturday, NPS rangers reported a small skier-triggered wind slab (40 ft wide, running 80 ft) wide on a north-facing aspect. North-facing aspects preserved soft snow.

Chalky-textured wind-loaded pillow near ridge-line adjacent to the skier-triggered wind slab. Photo credit: Sarah Crosier, Hurricane Ridge NPS

NWAC observer and NPS rangers on Thursday, 3/22 found blowing snow actively building fresh cornices and wind slabs above 5000’. Slabs were generally shallow, 6-8” (15-20cm), but were observed up to 1 foot (30cm) thick. Exposed windward slopes were often stripped of the new snow down to a firm and hardening crust.

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.