Wednesday April 11, 2018
Cornice Fall, Loose Wet, Wind Slab
Travel & Terrain Advice
Identify cornices and give them a wide berth when traveling either above or below.
Seek terrain options that minimize exposure and vulnerability to overhead hazard and travel on low angled terrain.
Avoid terrain traps that will magnify even the smallest of loose wet avalanches.
Avoid slopes with freshly load snow, especially during and immediately following wind and snowfall events.
Social media report of a skier accidental on a north aspect @ 1400 meters , not buried and no lost equipment but a close call. Loose wet late in the afternoon skiing alone and with out safety equipment, size one. Numerous loose natural avalanches on steep north aspects have been observed and where expected with the past warming and rain on snow events.
New snow and strong south east wind have and will continue to contribute to cornice growth and frailty and during the forecast period will become sensitive to human triggering. If trigger these hazardous features could when failing and falling onto the slopes below, then trigger either a wind slab or loose wet avalanche. Found at ridge tops on north aspects in predominately the alpine but also in isolated locations at treeline. These hazardous features will become very susceptible to triggering from light triggers such as mountain travelers and when triggered will be large to very large in size. Always give a wide berth when travelling either above or below cornices.
Past rain and forecast rain will unconsolidated the upper snow pack making it very touchy to human triggering. Found on all aspect and elevations, if trigger will start as a small avalanche but will gain mass becoming large and may have enough power to push a mountain traveler into or over terrain traps.
Strong south east wind and moderate to heavy snow fall will deposit up to 100 cm of new snow on lee aspects. These hazardous avalanche problems are located predominately in the alpine and treeline on all western aspects. Expect these avalanche to be touchy to very touchy to human triggering and if triggered will propagate far and wide and produce large to very large avalanches.
Warm temperatures and rainfall to above 2000 meters have moistened the snow surface on all aspects and elevations from the alpine . Tuesdays snowfall and strong south east winds have deposited in some areas to the lee of this dominate wind, pockets of up to 30 cm, all observed at the treeline. The march 22 melt freeze crust is down now between 90 to 135 centimeters and even though testing only reveals results in the hard range and resistant it still consistently produces a very planar shear. The lower snow pack continues to increase in strength and density.
|Surface||moist surface condtions|
|Upper||variety of new snow instabilities and density|
|Mid||march 22 melt freeze crust can be found down from 90 to 135 centimeters|
|Lower||well settled and dense|
Warm temperatures high freezing levels and precipitation amounts in the form of rain of up to 35 mm. Beginning early Tuesday, strong sustained south east winds continued most of the day combined with intermittent heavy snowfall. At days end, temperatures cooled and snowfall to 800 meters falling at a rate of 5 centimeters per hour was observed.
A parade of low pressure systems to the west of the region will bring to the forecast area, moderate to heavy snow fall , moderate to strong predominately south east wind and below seasonal temperatures.
Weather Forecast @1000 meters
Wednesday 15 to 30 cm new snowfall temp 1 , winds moderate to strong south east, freezing level to 1200 m.
Thursday 5 to 15 cm of snowfall temps -6 rising to 0, winds moderate south east, freezing level 0 m rising to 1000 m mid.
Friday 10 to 25 cm of snowfall and 10 to 25 mm of rainfall temps -1 to +3 winds moderate south east , freezing level 500 m rising to 1400 m mid day.
Posted on Wednesday April 11, 2018 by Jesse Percival