Avalanche Forecast
Issued: Jan 9th, 2016 10:00AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Wet and Wind Slabs.
NWAC,
Northwest Avalanche Center
The main problem on Sunday should be loose wet avalanches. It is a bit hard to say how extensive the loose wet avalanches will be so pay close attention to snow conditions if you venture out on Sunday.
Summary
Detailed Forecast
Sunny warmer weather should be seen on Sunday. It may be significantly warmer at higher elevations east of the crest.
The main problem on Sunday should be loose wet avalanches. It is a bit hard to say how extensive the loose wet avalanches will be so pay close attention to snow conditions if you venture out on Sunday. Possible loose wet avalanches should be mainly confined to steep southeast to southwest aspects during the late morning to early afternoon hours. Watch for surface wet snow deeper than a few inches, initial roller balls and initial small natural or triggered loose wet avalanches.
We have lowered the likelihood of triggering an older wind slab avalanche. But it will still be wise to watch for firmer wind transported snow on specific terrain features. The most likely locations are steep slopes below ridges mainly near or above treeline.
Some powder may still found out there on sheltered north slopes. Surface crusts will also abound to bring added enjoyment to your outing.
Snowpack Discussion
Fair weather for about a week over the New Year caused extensive surface hoar and near surface faceted snow. Then about 4-13 inches of snowfall over the east slopes last week buried the surface hoar and near surface faceted snow. Weak surface layers were seen in numerous reports both west and east of the crest in the Washington Cascades.
Tom Curtis was west of Blewett Pass on Iron Mountain, New Years Day and found the December 13 buried surface hoar layer 60 cm down that showed sudden collapses and propagation in several column tests with a firm slab. In this area the layer was prevalent on northeast to east aspects around 5300 feet near treeline. This may still be a layer of concern to track going forward in this specific area but no further reports have been received. This layer is likely gaining significant strength due to the mild temperatures this week.
PST End down, 60cm on 20151213 buried surface hoar layer. West of Blewett Pass, January 1, 2016. ENE aspect NTL @ 5330 feet. Photo: T. Curtis
Reports via the NWAC observations page for January 2nd at Blewett Pass, email received at the NWAC from Holden for January 3rd and further reports via the NWAC observations page for January 4th for Stevens and Snoqualmie, and most recently Tuesday the 5th on Red Mountain near Salmon La Sac (which includes a video) help confirm the extent of the recently buried surface hoar.
The North Cascade Mountain Guides were at Washington Pass on Friday found that the recent storm snow was surprisingly well bonded to the previous snow is spite of surface hoar and faceted snow at the interface. Tests and ski cuts gave no results due to little slab structure of the recent snow.
The DOT crew reported several small loose wet avalanches reached the shoulder of the highway on Saturday in Tumwater Canyon.
Problems
Loose Wet
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. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. 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.
Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.
Several loose wet avalanches, and lots of pinwheels and roller balls.
Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.
Aspects: South East, South, South West.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
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.
Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..
Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.
Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 10th, 2016 10:00AM
