Avalanche Forecast

Archived

Mar 9th, 2016–Mar 10th, 2016

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

Very strong winds and snow showers should combine to form new wind slabs on lee slopes, especially NW-NE facing. Watch for earlier storm slabs that may be masked by shallow colder surface snow. Dangerous avalanche conditions are expected near and above treeline Thursday.

Detailed Forecast

Yet another atmospheric river is slamming the Olympics Wednesday, bringing stormy wet weather with rising snow levels through Wednesday night.

The heavy precipitation at rising freezing levels should produce one or more natural avalanche cycles during the warmest periods, mainly Wednesday night.

By Thursday morning, cooling and light to moderate showers with continued very strong winds are expected.

The cooling should help wet snow to begin consolidating and cause a lowering danger during the day with shallow new snow accumulations expected.

However, near and above treeline, very strong winds should build new areas of wind slab on a variety of aspects, but mainly on NW-NE facing slopes below ridges.

Be especially aware that new shallow lower density snow may mask earlier storm slab formations, especially on slopes that did not avalanche overnight Wednesday.

Snowpack Discussion

Weather and Snowpack

Last week was wet and relatively mild with a series of active fronts transiting the region resulting in fluctuating freezing levels and periods of very strong winds.

A front Sunday brought about a foot of snow to Hurricane by Monday morning. No new snow was reported Tuesday morning.

A strong storm arrived midday Wednesday bringing heavy snowfall at rising temperatures and very strong south ridgetop winds.

The mid and lower snow pack in the Olympics should generally be a stable mix of crusts and layers of moist and rounded snow crystals.

Recent Observations

The ranger at Hurricane reported a foot of new snow on Monday morning with snow sliding off the road cuts and onto the road in many places. The Sunrise path on a northeast slope about a 1/2 mile from the visitor center released an avalanche that entrained snow to about 1' and became 100 feet wide although it could not be determined if it was a loose or slab avalanches due to low visibility.

On Tuesday the ranger added that there had been many 6-12 inch storm slab avalanches on Monday.

No observations from Wednesday, March 9.

Hurricane Weather Station

Internet communications to the station have been disrupted but will hopefully be restored soon. We are actively working on the solution.

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.