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Avalanche Forecast

Archived

Nov 26th, 2015–Nov 27th, 2015

Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.
Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.
Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.

Regions

Northwest Inland.

The snowpack is extremely variable depending on aspect and elevation and does not adjust well to rapid change. Watch for rising alpine temperatures to well above zero. Check out the Mountain Information Network. Give info, get info!

Weather Forecast

The above freezing layer will exist over the Northern regions through the forecast period. Temperatures could rise as high as 8 degrees above 1200 m and stay below zero with the outflow winds in the valleys. Patchy valley cloud may accompany the strengthening inversion as moisture becomes trapped. Ridgetop winds will generally be light and from the southwest.

Avalanche Summary

No new avalanches have been reported. Newly formed wind slabs may remain sensitive to human triggering and surface snow may start to deteriorate especially on solar aspects with the warming. Watch for obvious clues of instability like natural avalanches, snow balling and moist/ wet snow.

Snowpack Summary

The snowpack is extremely variable depending on aspect and elevation, with new wind slabs developing on reverse loaded southerly slopes and widespread surface crusts on all aspects at lower elevations. At upper elevations, last weekends storm likely produced stiff wind slabs on northerly aspects. The reactivity of these new wind slabs will likely change with elevation and underlying snowpack structure. The snowpack doesn't adjust well to rapid changes, so it may take several days to adjust and settle with the warm temperatures at higher elevations. Due to limited observations, I have very little confidence in what that underlying structure may be, although I suspect faceting, crusts and surface hoar may exist. How are they adjusting and reacting as shears? Are they distinct and reacting like a cash register when tested? Or are they becoming hard to find with resistant shear characteristics? If I were traveling in the mountains, I'd maintain a conservative and investigative approach and dig down to test for weak layers before committing to a slope.

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.