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Avalanche Forecast

Archived

Feb 24th, 2017–Feb 25th, 2017

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

Regions

Olympics.

Sunshine Saturday may lead to shallow wet snow conditions on steep solar aspects during the late morning to afternoon. Watch for snow rollerballs, snow falling from trees, and for wet surface snow more than the top few inches. 

Detailed Forecast

A brief period of high pressure should build over the area Saturday. This will allow for clearing and plenty of sunshine Saturday. Winds should remain light with very cool temperatures. 

Old wind slabs should continue to heal, becoming very isolated to specific terrain features, and very stubborn to human triggering Saturday. 

More sunshine is expected Saturday than any days this past week. Direct sunshine and some daytime warming should gradually increase the potential for loose wet avalanches Saturday, mainly confined to steep solar aspects during the warmest part of the day. Watch for wet surface snow deeper than a few inches if you find yourself on sun exposed slopes during any extended sun breaks.

Loose dry avalanches will also not be indicated as an avalanche problem. You can do tests for loose dry avalanches by pushing snow onto small safe test slopes.

Avoid areas along ridges where there may be a cornice and slopes below cornices, since cornices can fail at any time.

Snowpack Discussion

Weather and Snowpack

The latest of several warm, wet SW streams of moisture this season arrived on Valentines Day 2/14 bringing another round of heavy rain, avalanches, crusts and consolidation through Thursday 2/16 in the Olympics and Cascades. Minor snow was seen at Hurricane Ridge at the tail end of the storm.

A short period of fair weather on Friday, 2/17 caused another surface crust, especially on solar aspects.

Light amounts of new snow accumulated over the weekend. The NPS rangers reported 5 inches of snow Monday morning at Hurricane Ridge. 

A mix of sun and light snow showers Tuesday to Friday has freshened the surface snow daily, with up to a few inches of snow daily at cool temperatures and generally light winds.

This weather has all tended towards increased snowpack stability through the week, while maintaining some excellent touring conditions, especially on shaded terrain.

Recent Observations

NWAC pro observer, Matt Schonwald traveled to the Hurricane Hill region Friday 2/17. A hard, slick surface crust made travel precarious early Friday before the sun and warming began softening the crust. The few inches of snow fell during the tail end of the storm had bonded well and filled in many rain runnels, helping to smooth surface conditions. There was little evidence that the latest rain event produced any avalanches. The main hazard in the Hurricane area appeared to be an uncontrolled fall on the slick crust.

A report via the NWAC Observations page for Hurricane for 2/18 indicates a sizable loose wet avalanche on the W-SW side of Steeple Rock that probably occurred during the 2/14-2/16 period.

Another report via the NWAC Observations page for Mt Ellinor gives locally more snowfall and touchy avalanche conditions on Sunday 2/19. 

No observations have been received from the Olympics in the past five days.

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.