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Avalanche Forecast

Archived

Mar 19th, 2014–Mar 20th, 2014

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.

Expect possible new wind and storm slab layers on Thursday. Wet loose avalanches should also be possible in areas that receive significant new snow.

Detailed Forecast

Decreasing west northwest winds, with increasing light snow showers at cooler temperatures and low snow levels should be seen on Thursday.

New wind slab should be possible mainly on lee north to east slopes near and above treeline. Watch for cracking or firmer wind transported snow.

New shorter lived storm slab should also be possible on a wider variety of slopes mainly near and above treeline. This will be especially in areas that receive an inch of snow of more an hour for several hours.

The equinox is near and the sun is gaining power. Despite the cool temperatures and low snow levels wet loose avalanches seem possible in all the elevations bands. Watch for wet surface snow deeper than a few inches, pinwheels, and natural wet loose releases that usually precede more major wet loose snow avalanches.

The cooling trend should also build favorable stable new snow layers in many sheltered areas that receive light amounts of new snowfall.

Snowpack Discussion

The last stalled and moist frontal boundary draped mainly over the Olympics and north Cascades Saturday afternoon finally sagged south on Sunday, with rain generally changing to snow in a north to south fashion across the area.  A favorable temperature trend with gradual cooling occurred with this storm. The NWAC site at Hurricane picked up about 13 inches of snow late Saturday through Monday.

On Sunday NWAC observer Katy Reid reported likely wind slab layers on north to east aspects near tree line. She also reported possible storm slab layers on other aspects and possible wet loose conditions below tree line. She also reported consolidated and saturated layers in the mid and lower pack.

The increasing sun also activated surface snow on Sunday. A Park ranger reported a backcountry skier on Sunrise Ridge above the road Sunday afternoon triggered a storm slab about 15-20 feet wide that covered the uphill lane.

Little avalanche activity was reported on Tuesday in the Cascades, mainly small wet loose avalanches such as from NWAC observer Dallas Glass at Stevens and the Alpental ski patrol.

The next cold front is crossing the Northwest on Wednesday. This is causing increasing winds, rain and snow and a cooling trend on Wednesday. Hurricane Ridge should have a few inches of new snow on Thursday morning.

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.

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.