Avalanche Forecast
Issued: Feb 8th, 2019 10:25AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Loose Dry.
NWAC,
Northwest Avalanche Center
A cold, potent storm will continue to bring new snow, increasing winds, and poor visibility over the next 24 hours. Dangerous avalanche conditions will develop at upper elevations. Avoid freshly wind loaded slopes and terrain features 35 degrees and steeper.
Summary
Discussion
On Friday, 4in of cold, dry snow accumulated in the Mt. Baker area. Light snowfall should continue overnight and into Saturday. For once, Mt. Baker looks to receive less snow than many other areas throughout the region. Strong winds, however, will primarily drive the avalanche hazard. Cold, arctic airflow out of interior British Columbia will surge down the Fraser River Valley bringing gusty northeast winds.
Expect blustery conditions and fresh wind slab formation Saturday. New and wind-blown snow will be deposited on a variety of old, weak snow surfaces. It will be crucial to monitor changing conditions throughout the day, and carefully assess the new/old snow interface. In wind-sheltered areas, loose dry avalanche concerns may develop as more snow accumulates.
Observers found blowing snow and cracking in fresh, shallow wind slabs in the Bagley Lakes area on Friday. On Thursday, a skier triggered a small slab avalanche in steep terrain on a north aspect at 5500ft in the Mt. Baker area. (observation) The avalanche failed within recent snow from Monday. This lingering storm instability buried less than 1ft deep appears stubborn to trigger and isolated, but it has been found in the Hwy 20 area as well. (observation) Evaluate the upper snowpack carefully as winds and new snow form stiffer, thicker slabs above this interface.
Snowpack Discussion
Regional Synopsis Coming Soon
Problems
Wind Slabs
Plenty of low-density snow is available for transport. Strong northeast winds beginning Friday night will redistribute the new snow and form fresh wind slabs. These slabs will build atop weak old snow surfaces. You will encounter the problem in exposed terrain at mid and upper elevations. Be careful near ridgelines and around convex rollovers. Look for signs of instability like collapses and shooting cracks. Watch for blowing snow, textured snow surfaces, and lens-shaped pillows to help identify wind slabs. Seek out wind-sheltered our scoured terrain to avoid the problem.
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: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Dry
The new snow is light and cohesionless. Watch for triggering loose dry avalanches on slopes 35 degrees and steeper. These avalanches are easy to predict as they break at your feet. Use caution around terrain traps like cliffs, gullies, or rocky slopes. Use small test slopes to check if the surface snow slides easily.
Release of dry unconsolidated snow. These avalanches typically occur within layers of soft snow near the surface of the snowpack. Loose Dry 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. Loose Dry avalanches can trigger slab avalanches that break into deeper snow layers.
Loose Dry avalanches are usually relatively harmless to people. They can be hazardous if you are caught and carried into or over a terrain trap (e.g. gully, rocks, dense timber, cliff, crevasse) or down a long slope. Avoid traveling in or above terrain traps when Loose Dry avalanches are likely.
Loose Dry avalanche with the characteristic point initiation and fan shape.
Loose dry avalanches exist throughout the terrain, release at or below the trigger point, and can run in densely-treed areas. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells.
Elevations: Below Treeline.
Likelihood
Expected Size
Valid until: Feb 9th, 2019 10:25AM
