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Avalanche Forecast

Archived

Mar 21st, 2016–Mar 22nd, 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 unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

A mix of spring avalanche problems exists with no one problem dominating. Evaluate the local snow and terrain carefully on Monday.

Detailed Forecast

Light to moderate west winds and up to a few inches of new snow should be seen in the near and above treeline zone at Hurricane Monday night and Tuesday. Temperatures should continue to slightly cool from the previous couple days.

This weather may build new, small shallow wind slab on lee slopes in the near and above treeline through the day light hours on Tuesday. This is most likely on N-SE slopes. Firm wind transported snow and snowpack cracking can be good signs of wind slab layers.

Continued wet snow conditions can't be ruled out on Tuesday. The cooler temperatures should limit this problem to the below treeline. Watch for wet snow deeper than a few inches and pinwheels or natural releases.

Recently formed cornices have grown large and can become sensitive following nights with above freezing temperatures.  Avoid areas on ridges or summits where there may be a cornice and avoid slopes below cornices. Cooler temperatures Tuesday may help to temporarily strengthen cornices Tuesday.

Snowpack Discussion

Weather and Snowpack

A combination of sun and mild temperatures for several days gave way to warm temperatures and light rain Sunday 3/20. This weather caused the 2-3 feet of storm snow that fell at Hurricane about March 9-15 to settle, consolidate and stabilize. Recent sun, warmth, freezing and rain drastically changed snow conditions. Surface snow conditions have become highly variable, ranging from some well settled old snow on steep shaded slopes and a mix of surface crusts, wind buffed surfaces or shallow wet snow on other aspects.

The most recent storms did build large cornices along ridges with several releases noted over the past few days.

Moderate to somewhat strong southwest winds were seen Sunday night and a couple inches of new snow was reported by the ranger at Hurricane on Monday morning. Some new, small shallow wind slab might be possible above treeline.

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

Recent Observations

A Hurricane Ridge Park ranger found variable surface crusts Saturday morning, as overnight temperatures remained well over freezing. Similar conditions were found Sunday with the snowpack settling an additional 20 cm (8 inches) at Hurricane Ridge since Saturday morning, an additional sign of a strengthening snowpack.  

Hurricane Weather Station

Internet communications to the station have been disrupted at the NWAC office. The ISP inadvertently disconnected our service and we are anticipating a resumption of service soon. We apologize for the outage and thank you for your patience.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.