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Avalanche Forecast

Archived

Feb 6th, 2016–Feb 7th, 2016

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

Olympics.

Lingering wind slab on lee slopes near and above treeline may be tougher to trigger, but still possible on Sunday. Wet loose avalanche potential will vary considerably by how the weather forecast plays out. Moderate avalanche danger means heightened avalanche conditions (hazard) on specific terrain features, so match your terrain selection to the avalanche problems.  

Detailed Forecast

A warm front lifting north across the area should bring light rain and clouds to the Olympics Sunday. A warming trend will begin Sunday, but will likely be tempered by breezy winds near and above treeline and extensive cloud cover. However, there is a decent amount of uncertainty for Sunday's forecast.  

Lingering wind slab on lee slopes in the near and above treeline elevation bands may be tougher to trigger, but still possible Sunday. Watch for signs of snowpack cracking and firmer wind transported snow on lee slopes.

Wet loose avalanche potential will vary considerably by how the weather forecast plays out Sunday. Light rain will encourage natural wet loose activity on steeper slopes. Be aware of loose wet avalanche potential above terrain traps (like above cliffs or near gullies), where even small wet avalanches can become powerful and have unintended consequences.  

Snowpack Discussion

The last heavy rain fell in the Olympics January 27th-28th with over 2 inches of rain recorded at the NWAC station at Hurricane Ridge.

A strong occluded front with strong winds crossed the Northwest January 29-30th. Hurricane Ridge had about 14 inches snowfall.

NWAC pro-observer, Matt Schonwald visited Hurricane January 29th and found rapidly building wind slab and extensive loading on lee slopes in all 3 elevation bands. New cornices were sensitive to triggering but still relatively small. 

Cool, benign weather followed Sunday through Tuesday. A sun crust formed on many solar slopes and surface hoar was seen on many non-solar slopes in the Cascades so this is possible in the Olympics as well.

A cold front and then a warm front crossed the Northwest on Wednesday and Thursday. The Hurricane ranger reported about 8 inches of snowfall for the 2 days ending Friday morning. No snowpack observations were received Friday due to the closed road. 

An additional 7 inches of snow fell with a cooling trend during Friday night's fast, yet powerful front. Lee slopes were likely loaded by strong S-SW winds with this system. 

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.