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Avalanche Forecast

Archived

Dec 24th, 2013–Dec 25th, 2013

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

Regions

Olympics.

Detailed Forecast

Mostly sunny days and fair nights are expected. Winds should remain light with mild temperatures Christmas Day. This should allow for some surface snow melt on sun exposed terrain. Some shallow wet snow conditions may develop by late morning or afternoon on some of these steep sun facing slopes where caution should be exercised. 

Snowpack Discussion

The last significant snow occurred in early December. Either strong high pressure or systems with high freezing levels have limited the snow accumulations in the Olympics and specifically at Hurricane Ridge where the total snowdepth remains a meager 12 inches. NWAC weather station at Hurricane has recorded less than 2 inches of water through December. 

The overall shallow snowpack is limiting the avalanche danger, especially near tree line and below tree line where significant terrain and vegetative anchors remain. Field observations to Klahhane Ridge Sunday indicated that the lack of snow indeed is limiting the danger on most slopes. On north facing slopes below the ridge there was evidence of wind slab or wind drifts ranged to over 1 meter but most areas have mostly 30-75 cm (1-2+ ft) of snow depth. Rain to high elevations and lack of recent snow is maintaining mostly stable conditions with surface crusts or shallow wind drifts over crust layers.

 View from Klahhane Ridge south facing slope, Olympics 12-22-2013, K. Reid

View looking east along Klahhane Ridge, Olympics 12-22-2013, K. Reid

 

Watch for areas where a locally deeper snow pack may exist. The most likely areas to find any unstable conditions would be on steep generally northerly facing terrain below ridges above tree line. In these areas, some wind slab may be present.  

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.