Avalanche Forecast

Archived

Jan 16th, 2014–Jan 17th, 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

Stevens Pass.

The avalanche danger should continue to slowly diminish Thursday. But watch for lingering wind slab in the alpine and loose wet snow on steep solar slopes.

Detailed Forecast

Light winds, sunny weather and warm temperatures should be seen on Thursday. But the sun is still pretty weak less than a month after the solstice.

This weather should mainly cause layers to further consolidate and further stabilize. Watch for lingering cornices and areas of wind slab on lee slopes mainly in the alpine. This should be mainly on north to southeast facing slopes.

Warming and sunshine may lead to loose wet snow conditions on steeper solar aspects.

Snowpack Discussion

Weather:

A nearly week long major storm cycle ended about Tuesday morning.

This first part delivered heavy snow with about 1.5-4 feet of snowfall for a 4 day period ending Sunday morning at NWAC sites near and west of the crest.

Then a strong warming period with wet snow and rain was seen with rain or water equivalents in the 1.4-3.5 inch range for 2 days ending Tuesday morning at most NWAC sites near and west of the crest.

Avalanches:

An avalanche cycle was seen during the warming period as increasing wet heavy snow and then rain built an upside down snowpack and loaded underlying colder and sometimes preserved lower density layers.

The main avalanche action was Sunday. Very large natural D3 avalanches were seen on the north slopes of Shuksan Arm. A very large D3 natural avalanche was reported by the DOT from a path known as West Camp on Rock Mountain near Stevens Pass starting at about 5900 feet. A snowcat triggered a 5 foot slab avalanche at White Pass down to September faceted snow on an east slopes at 5700 feet. Other signs of instability such as shooting cracks and wind and storm slab avalanches up to size D2 were reported from the west side of Mt Baker and Stevens and Snoqualmie.

From the west side of Mt Baker on Sunday by NWAC observer Jeff Hambleton.

Warming and additional rain was seen on Monday. Wet or saturated snow up to 1 meter depth coupled with sunshine and warming produced up to D2 wet snow avalanches on solar slopes at Stevens.

Photo from the Smithbrook area near Stevens on Tuesday by NWAC observer Dallas Glass and

a short video of the wet loose slides: https://www.youtube.com/channel/UCXKN3Cu9rnnkukkiUUgjzFQ

Consolidation and a new surface crust from Tuesday night has helped to improve stability by Wednesday. No further avalanches are reported by the ski areas on Wednesday.

For the Olympics and west slopes of the Cascades a generally favorable mid and lower snowpack exists, even if well below seasonal norms, and is expected to consist of crust layers and melt form crystals from warm periods in late December and early January.

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.