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Avalanche Forecast

Archived

Mar 16th, 2017–Mar 17th, 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 possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

The stability of the Olympics snowpack has greatly increased after avalanche cycles and consolidation the past week. You should mainly need to watch for previous slab at higher elevations and the development of loose wet avalanches at lower elevations on Friday.

Detailed Forecast

A low pressure system is expected to form well to the SW of track towards the central Washington coast on Friday, before moving inland Friday night. This system should spread increasing light precipitation to Mt Hood Friday morning, before spreading to the remainder of the forecast area Friday afternoon, with rising snow levels. The peak in winds, snow levels and precipitation are expected Friday night into early Saturday morning.

At Hurricane previous wind slab is most likely to linger on NW to SE aspects due to previous SW-W winds. But watch for firmer wind transported snow on other aspects especially in areas of complex terrain.

Small loose wet avalanche conditions are most likely to linger at lower elevations or to develop as rain moves in on Friday afternoon. Watch for surface wet snow deeper than a few inches, rollerballs or increasing small natural releases.

Although the likelihood of wet slab or glide avalanches has greatly decreased, continue to avoid unsupported slopes where you know there is a smooth underlying surface, or slopes with glide cracks.

It is always a good plan to avoid areas on ridge where a cornice maybe present and slopes below cornices.

Remember to re-evaluate plans if weather conditions are different or deteriorate sooner than expected.

 

Snowpack Discussion

Weather and Snowpack

The first week or so of March was very cool and snowy. It looks like Hurricane had about 40-50 inches of snowfall during this period.

A strong frontal system brought increasing precipitation, winds and warming trend to the Olympics and Cascades on Thursday 3/9. On Thursday night rain fell  up to about 5000-5500 feet in the Olympics. Natural and skier triggered avalanches were reported at Hurricane on Friday 3/10. 

Moist W-SW flow and a stalled frontal boundary have produced periods of moderate to occasionally heavy rainfall at most locations throughout the Olympics and the west slopes of the Cascades on Monday through Tuesday.

The past week of weather has done a reset of the snowpack in the Olympics and along the Cascade west slopes. These areas at the end of Thursday have light amounts of new snow over a firm, consolidated, stabilized snowpack.

Recent Observations

No recent observations.

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.