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Avalanche Forecast

Archived

Mar 27th, 2016–Mar 28th, 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 unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

A mix of dangerous winter and spring avalanche conditions is likely to linger in the near and above treeline at Hurricane following weather and snowfall on Sunday.Your ability to identify and avoid avalanche problems will be essential on Monday.

Detailed Forecast

An upper ridge and surface high pressure should begin to strongly build west of the US west all the way to the Gulf of Alaska on Monday. Light snow showers over the Olympics should end Monday morning. There should be several inches of new snow at Hurricane Monday morning from Sunday.

A mix of likely dangerous winter and spring avalanche conditions is likely persist in the near and above treeline at Hurricane on Monday. The sun is getting much stronger and new snow will be reactive to solar effects.

Loose wet avalanches should be likely especially on solar slopes on Monday. Avoid avalanche terrain if you start seeing pinwheels or initial small natural loose wet avalanches. Be aware of terrain traps where even a small loose wet avalanche could have unintended consequences.

New wind slab of a foot or more is likely on lee slopes mainly in the near and above treeline on Monday. This is most likely on north to east slopes but possible on other aspects. Watch cracking and firmer or chalky wind transported snow. Remember that snow pits may not be helpful due to variability in the snowpack.

New storm slab layers may linger into Monday where there was rapidly accumulating snow for more than a few hours on Sunday. Pay special attention to slope convexities where storm slab is mostly likely to be triggered.

Cornices have grown large recently. Cornices can break much further back on ridges than expected and releases can be unpredictable during the spring.

Snowpack Discussion

Weather and Snowpack

Snow accumulations Wednesday to Friday following the last front were about 4-6 inches at Hurricane with new snow of over a foot on wind loaded slopes near treeline. This snow should have bonded well to a moist crust buried March 22nd.

A strong front and upper short wave crossed the Northwest Sunday morning. This is being followed by a large upper trough and cool unstable air mass Sunday afternoon and evening.

Frequent March storms have built large cornices along some ridges in the Hurricane Ridge area.

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

NWAC professional observer Matt Schonwald toured in the Hurricane Ridge area Friday.  Matt generally found the new storm snow unreactive in snowpit tests and with ski cuts on test slopes. No recent avalanches were observed in the Hurricane Ridge area. Wind effects were limited to directly below ridgelines, with generally settled powder and good skiing found on non-solar aspects with less wind effect. Area cornices were firm and unlikely to trigger.

The road to Hurricane Ridge was closed on Sunday. But the Park Service reported that hikers heard natural avalanches in the vicinity of Lake Angeles a few miles northeast of Hurricane. Details were not available due in part to low visibility.

Hurricane Weather Station

Internet communications were restored to the station on 3/23!  Thank you for your patience. 

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.

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.