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Avalanche Forecast

Archived

Feb 21st, 2016–Feb 22nd, 2016

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.

The avalanche danger should gradually decrease on Monday. Watch mainly for new or previous wind slab on the lee slopes near ridges or mid-slope where cross loading may have occurred.

Detailed Forecast

West winds and snow showers should taper off on Monday with lower snow levels. The avalanche danger should gradually decrease on Monday.

The winds and snow Sunday and Sunday night may have built new shallow wind slabs on lee slopes mainly near and above treeline. Older wind slab may linger on similar slopes. Watch for new or previous firmer wind transported snow mainly on the lee N to SE slopes near ridges or mid-slope where cross loading may have occurred.

New shallow storm slab is possible if you are in an area where more than several inches of snow rapidly accumulated Sunday to Monday morning.

Snowpack Discussion

Weather and Snowpack

Heavy rain and mild temperatures dominated last Sunday and Monday forming the latest crust in the Olympics. There was about 1. 5 inches of rain at Hurricane over the 2 days ending Tuesday morning.

An active and at times stormy, cooler pattern began to bury the crust on February 17th and brought about 10 inches of snow to Hurricane Wednesday to Friday. Another front is crossing the area on Sunday followed by a short wave Sunday night that will cause shifting winds and a few inches of snow.

The mid and lower snow pack in the Olympics should be a stable mix of crusts and layers of wet rounded snow crystals.

 Recent Observations

Professional NWAC observer, Matt Schonwald was at Hurricane Ridge on Friday. Recent storm snow deposits of about 4-6 inches had accumulated in wind sheltered locations. Very strong southerly winds were building shallow wind slabs on lee slopes near tree line below ridges and also building small cornices. Matt recommended giving new wind slab a wide berth.

A small wind slab was triggered on  a lee slope called Sunrise Slope on Saturday although details are not available.

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.

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.