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Avalanche Forecast

Archived

Mar 15th, 2014–Mar 16th, 2014

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.

Avalanche danger should increase during the day on Sunday. Watch for areas of newly forming wind slab on lee easterly aspects near and above treeline.  Cooling should help limit wet loose avalanche concerns but the potential remains below treeline so watch for shallow wet snow on steeper terrain.  

Detailed Forecast

A front band of precipitation and strong winds should stay draped over the US/Canadian border overnight and early Sunday, producing moderate precipitation at gradually lowering snow levels for the Olympics by Sunday.   

Snow levels lower through the day Sunday with rain or snow changing to showers and gradually decreasing. This should maintain some wet snow conditions below tree line Sunday.  However strong winds and new snowfall should build some areas of wind slab on lee northeasterly to southeasterly aspects in this region near and above treeline. 

Snowpack Discussion

The most recent week long storm cycle occurred in early March and wound down last Sunday. This storm cycle deposited about 4 inches of water and 2 feet of snow at Hurricane Ridge. This cycle was warmer and featured mainly wet snow and rain leading to several natural avalanche cycles during the first week of March.  Average freezing levels have been roughly 2000-3000 feet higher thus far in March versus February! 

NWAC observers Tyler and Katie Reid last Friday at Hurricane reported wet and saturated upper snow pack layers and numerous wet loose avalanches to size 2. Warming effects had penetrated quite deeply into upper snowpack layers. Here is a video from Tyler and Katy at Hurricane from last Friday. Warm wet weather last weekend caused wet snow conditions and many wet loose avalanches at Hurricane with several cornice collapses as well as reported by NWAC observer Katy Reid on Sunday.

Several large and destructive wet slab avalanches released down to old facet/crust combo from earlier this winter naturally and with explosives early last week over the west slopes of the Cascades. It is unknown if any avalanches this large occurred in the Olympics. 

A NPS ranger reported a few inches of new snow over a firm crust late Friday morning at Hurricane Ridge.  A few more inches of snow likely accumulated during the day down to around 4000 feet with some wind transported snow likely near treeline due to moderate westerly winds.

Surface snow melt due to filtered sun and mild weather Saturday where countered by the cooling effects of strong winds.  This should have maintained mostly firm crust layers with only shallow surface melt.  Precipitation was delayed Saturday with only light amounts falling during the day and thus had little affect on the danger significantly changing as earlier forecast. 

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.