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Avalanche Forecast

Archived

Jan 26th, 2016–Jan 27th, 2016

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

Regions

Olympics.

In the Olympics the main problem should continue to be loose wet avalanches on Wednesday. Watch for wet surface snow deeper than a few inches and pinwheels or roller balls that usually precede loose wet avalanches.

Detailed Forecast

A break between frontal systems should be seen most of the daylight hours on Wednesday with continued mild temperatures.

In the Olympics the main problem should continue to be loose wet avalanches on Wednesday. Watch for wet surface snow deeper than a few inches and pinwheels or roller balls that usually precede loose wet avalanches. This may be most likely on non solar slopes holding loose snow but will be indicated on all aspects. Solar effects or sun breaks should increase the chance of loose wet avalanches.

Previous wind slab in the above treeline may be loaded and weakened by wet surface snow. This avalanche problem may be getting unlikely but watch for signs of previous firmer transported snow mainly on northwest to southeast aspects.

Rapidly increasing rain should begin in the Olympics around sunset on Wednesday. Be prepared to change your plans if the rain begins sooner than expected and you see signs of increasing instability or avalanches.

 

Snowpack Discussion

A warm front last Thursday caused heavy rain in the Olympics and this caused a loose wet avalanche cycle on steep slopes in all the elevation bands.

This was followed by cooler weather and some snow. The cooling formed good bonding to the forming crust as observed by NWAC pro-observer Matt Schonwald Friday.

Matt reported generally stable surface snow conditions with no layers of concern in the BTL and NTL elevation zones. Overall the snowpack consisted of a few inches of saturated snow, well bonded to supportive dryer, old snow and a newly forming crust. Stability tests were all negative. Some transport of loose surface snow was seen being deposited on the northerly facing terrain below ridges, but no distinctive wind slab had formed as of Friday afternoon.

A weakening front is crossing the Northwest today with high snow levels and rain in most areas.

Hurricane Ridge weather station: NWAC forecaster Garth Ferber was at Hurricane Ridge Thursday and with the help of NPS IT staff our weather station is back online!  We appreciate everyone's patience and the new internet connection to the weather station should be more reliable than the previous aging microwave system.

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.