Avalanche Forecast

Archived

Feb 20th, 2023–Feb 21st, 2023

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

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.

Regions

Glacier.

EVERYONE!! STAY OUT OF WINTER PERMIT AREAS WHEN THEY ARE CLOSED!!!

People have entered closed areas (Griz Shoulder, Hourglass) 3 days in a row and the winter permit system is in danger of being shut down!

Speak up out there! Let violators know they are jeopardizing their lives from artillery, and everyone's access!

Confidence

Moderate

Avalanche Summary

Artillery control had good results Sunday night...notably Camp West, sz 4, had large timber knocked down across the highway.

On Sunday the field team remote triggered from ridge-top several storm slabs in steep gully features at Fidelity, sz 2-2.5, with crown depths of 30-40cm.

Touchy storm slabs were reported in the Asulkan near the hut, with unsupported rolls shedding sz 2-2.5 slabs.

Snowpack Summary

45cm of storm snow fell Sunday night, 65-80cm the last 2 days, along with mod-strong W'ly winds. Fresh storm slabs blanket the Alpine and exposed Treeline features. Low-density, deep snow is found in sheltered areas.

Several thin crusts are buried below the storm snow on steep solar aspects.

The deep persistent weakness at the base of the snowpack (rounding facets and a crust in some locations) has been showing signs of strengthening recently.

Weather Summary

Wild weather coming at us Monday night! An intense frontal passage will bring strong SW winds and high snowfall rates, then abruptly Tues AM, snowfall stops, winds flip to the E, and temps will drop 10 to 15 degrees.

Tonight: heavy snow, 25cm, strong gusty SW winds, Alp high -6*C

Tues: Isolated flurries, Alp high -16*C, light E winds

Terrain and Travel Advice

Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Loose avalanches may start small but they can grow and push you into dangerous terrain.
Avoid exposure to slopes that have cornices overhead.

Problems

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 Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.