Avalanche Forecast

Archived

Nov 27th, 2016–Nov 28th, 2016

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

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Watch for previously formed wind slab layers on Sunday especially in the northeast to central east zones. Be prepared to ratchet back your plans if conditions get stormy again before the end of the daylight hours on Sunday.

Detailed Forecast

Forecast for the Cascade East Slopes

A relative short break in the weather should be seen much of Sunday so conditions shouldn't change too much on Sunday.

There is still a lot of variation in snow cover depending on elevation since it is early in the year. Expect winter conditions at the higher elevations and too little snow for avalanches at the low elevations.

While this forecast is for a moderate avalanche danger mainly above tree line the report above sure indicates you better be watching for potential wind slab. The potential for triggering does not seem great but such an avalanche can have deadly consequences. Watch for signs of firmer wind transported snow.

Note that the next system is due to begin to arrive late in the day on Sunday. Be prepared to ratchet back your plans if conditions get stormy again before the end of the daylight hours on Sunday.

Snowpack Discussion

Weather Discussion for the Cascade East Slopes

There has been a lot of variation depending on location in weather and snow conditions in the Olympics and Cascades the past couple days.

Moderate snow has fallen the past few days in the northeast and north part of the central east zones. But direct measurements have been somewhat lacking as the weather station gremlins have been having their fun the past few days at the NWAC and NRCS Snotels.

Less snow has fallen lately in the southeast zone.

Decreasing south winds and a cooling trend should be seen on Saturday as a weakening front shifts to the east. Some light amounts of snow seem likely along the east slopes.

Recent Reports for the Cascade East Slopes

There are few recent reports for the Cascade East Slopes. However on Friday a skier triggered a deep wind slab on a 40 degree northwest slope at about 7500 feet on Slate Peak near Harts Pass. The crown varied from about 2 to 7 feet and ran about 2-300 vertical feet with car sized chunks of debris. Fortunately the skier was not caught. He noted that windward slopes across the valley were scoured indicating recent wind transport.

There are currently no indications of any persistent weak layers along the Cascade east slopes.

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.

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.