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Archived

Avalanche Forecast

Apr 10th, 2018–Apr 11th, 2018
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Olympics.

Light snow and moderate winds will create heightened avalanche danger on wind loaded slopes near and above treeline Wednesday. Use visual clues such as fresh cornices, wind drifted pillows and cracks in the snow all indicating that you could trigger a Wind Slab avalanche. Small Loose Wet avalanches are possible below treeline in isolated areas. 

Detailed Forecast

Light snow and moderate winds will create heightened avalanche danger on wind loaded slopes near and above treeline Wednesday. Use visual clues such as fresh cornices, wind drifted pillows and cracks in the snow all indicating that you could trigger a Wind Slab avalanche. 

Generally safe avalanche conditions are expected below treeline but small Loose Wet avalanches are possible in isolated areas. Watch for signs of wet snow conditions such as sluffing, roller-balling and any natural Loose Wet avalanches. Avoid terrain traps if you suspect you could trigger a Loose Wet avalanche. 

Snowpack Discussion

A front brought rain and wind to Hurricane Ridge Tuesday. Warm and dry conditions were seen on Monday. A strong storm over the weekend caused rain Saturday to high elevations followed by cooling and new storm snow of around a foot by Sunday afternoon. The weekend snow built fresh Wind Slabs on a variety of aspects, especially below ridges and cornices along exposed ridges. 

Older weak snow had been observed on N-E aspects near and above treeline above a crust prior to this weekend's storm about 1-1.5 ft below the surface. This interface is likely no longer an issue due to recent rain and warm temperatures. 

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

Observations

Park rangers reported about 1 ft of new snow as of Sunday morning.

On Friday 4/6, NWAC professional observer Matt Schonwald found the facets above a crust on NE aspects between 5200-5400 ft healing.  While this interface may have come into play with Wet Slabs last Saturday, the Persistent Slab problem has ended. Matt also found glide cracks in isolated areas. The snowpack on solar aspects is becoming patchy, especially below treeline. 

Avalanche Problems

Wind Slabs

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.

 

Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..

 

Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.

 

Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 1