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Avalanche Forecast

Archived

Dec 5th, 2017–Dec 6th, 2017

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Olympics.

Watch for small areas of firmer, wind-transported snow on isolated, lee terrain features. Watch for loose-wet snow avalanches releasing from sun exposed rock faces or below cliffs or rock bands.

Detailed Forecast

Continued sunny and mild weather is expected Wednesday with some moderate easterly winds near ridges.

Recent snow layers will continue to stabilize in the Hurricane Ridge area. 

Small wind slabs may form on a variety of aspects, mainly on exposed lee slopes receiving any transported snow. These wind slabs are expected to be stubborn or difficult to trigger. Watch for small areas of firmer, wind-transported snow on isolated, lee terrain features.

Continue to watch for isolated, small, loose wet avalanches on steep sun exposed terrain during the late morning or afternoon, especially on unsupported slopes or near rocks.

Early season terrain hazards still exist, such as poorly covered rocks, vegetation and creeks, particularly at lower elevations.

Snowpack Discussion

Warm, very wet weather before Thanksgiving caused wet snow and glide avalanches as well as snowpack consolidation, leaving a strong crust as a gift. There are no snowpack concerns below the Thanksgiving crust and in general new snow received post-Thanksgiving has reportedly bonded well.

A series of frontal systems produced snow over the week following the Thanksgiving warm period: Hurricane Ridge received about 2 feet of snow.

This includes the most recent snow of about 10 inches received at Hurricane Ridge ending Sunday morning, December 3.

Increasingly fair weather Sunday through Tuesday has allowed for a slow decrease in danger with about 2-4 inches of snowpack settlement noted at the Hurricane weather station.

Observations

No observations have been received since Sunday.

Friday morning: NPS rangers reported 5" of new snow along with active wind transport of the new snow. 

Saturday morning: NPS rangers report 7" of new snow. Small, 15 cm deep natural storm slab avalanches were being triggered by tree bombs along the road. Snow pit tests on a north slope at 5200' gave ECTP2 and ECTP4 @ 10 and 15 cm, respectively. Clean propagation was observed in both cases. On this test slope, the pencil hard Thanksgiving rain crust was down 55 cm.

On Sunday morning, the Hurricane Ridge rangers report small, loose dry avalanches along the road with no slab character. Ski penetration was 6" with generally right-side-up near surface snow.

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.