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Avalanche Forecast

Archived

Mar 5th, 2014–Mar 6th, 2014

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

Dangerous avalanche conditions should persist Thursday, especially above treeline where the strongest winds are expected and where weaker bonds to the early March crust should remain. 

Detailed Forecast

Another strong warm front should cause more moderate to heavy rain or snow at higher snow levels Wednesday night with a bit of a break Thursday morning.  Another front should renew moderate rain or snow at lower snow levels during the day Thursday along with strong winds. 

Five day water equivalent nearing 2.5-3 inches and snowfall of about 1.5-2 feet should be the expected storm totals in the Hurricane Ridge area ending Thursday afternoon.

Due to rain continuing to reach higher elevations Wednesday night before gradually cooling Thursday, continued  wet loose avalanches remain a concern at mid and lower elevations.  This should be at least up to the near treeline zones. Steep slopes that recently received heavy snowfall should be primed for wet loose avalanches. Natural snowballing and natural releases are usually precursors to this type of avalanche.

Wind slab will be a likely concern mainly on lee slopes above treeline but gradually lowering to near treeline as cooling occurs Thursday. This should be mainly northwest to southeast aspects. Watch for signs of wind transported snow, such as trees void of snow and sculpted surface snow patterns and deposited pillows of denser wind slab.

Storm slab will also be listed as a concern above treeline on a wider variety of aspects. Wetter denser new snow accumulating over lower density snow in the above treeline zone will contribute to this concern.

Snowpack Discussion

Recent Weather

A two week storm cycle ended a week ago causing about 9 feet of snowfall and produced many avalanches at Hurricane Ridge.

Warm dry weather was seen late last week Wednesday to Saturday causing wet snow avalanches and melt/freeze crusts at Hurricane Ridge and throughout the region. 

The series of storms began Sunday March 2nd and have been moving through daily over the past four days.  There has been about 1-1.5 feet of new snow deposited at Hurricane Ridge during these storms with some periods of rain reaching to near 6000 feet at times.   

Hurricane Ridge

NWAC observer Tyler Reid at Klahhane Ridge last Friday found plenty of wet unconsolidated snow on solar aspects below tree line. Some small surface hoar growth was noted in places - video from Friday.

On Saturday, a ranger and Tyler reported a very hard surface crust had formed as a result of the significantly colder overnight and early morning temperatures.

The latest storm cycle that began on Sunday likely produced an avalanche cycle at Hurricane Ridge similar to the Cascades Sunday night and Monday morning.  Though no first hand observations have been made, poor bonds to the melt-freeze crust from late last week will likely have provided bed surfaces and weak layers for storm slab failures.

Snow levels have been rising and temperatures warming with increasing instability and avalanches similar to the Cascades on Tuesday afternoon and again Wednesday however we are still in the dark, so to speak, with no observations from the Hurricane Ridge area or anywhere else in the Olympics.

The mid and base pack around Hurricane Ridge should still consist of stable crusts and melt form layers from periods of warm weather earlier this winter. Also in the below tree-line zone on solar aspects rain and mild temperatures may keep the shallow snowpack wet and unconsolidated. 

Problems

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.

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.