Friday April 13, 2018

Sunday April 15, 2018
Saturday April 14, 2018
Friday April 13, 2018
Confidence: Moderate - numerous weather scenarios and differing forecast outcomes.

Main Concerns

Cornice Fall, Loose Wet, Wind Slab - view Avalanche Problems for detailed information.

Travel & Terrain Advice

Identify and choose terrain options that avoid areas with freshly wind loaded snow and cross loaded features.

Caution when travelling either above or below cornices.

Make careful and cautious terrain choices when rain on snow events occur, temperatures warm rapidly or during any appearance of the sun.

Avalanche Summary

No new natural avalanches reported

Avalanche Problems

Cornice Fall

New snow and strong south south west wind 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 all 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 provide a wide berth when travelling either above or below cornices.

Loose Wet

Past rain and forecast rain will unconsolidated the upper snow pack making it very touchy to human triggering. Found on all aspect and predominately at treeline and below, will if triggered 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.

Wind Slab

Past Strong south east wind and forecast strong south west wind combined with 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 both western and eastern 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.

Snowpack Summary

Variable surface conditions, scoured at ridge tops in the alpine and at treeline, wet down 30 cm below treeline. Lee slopes at tree line from strong past south east winds have been observed with wind slabs above 50 cm and these wind slabs are suspected to have breached 100 cm in the alpine. This new wind effected snow overlies previous moist and wet snow. The March 22 melt freeze crust can be found down between 90 and 150 cm. the lower snow pack is well settled and dense.

Snowpack Details

Surfacenew snow, breakable crust and moist conditions all dependent on elevation
Uppermoist and wet snow
Midmarch 22 melt freeze crust can be found down from 90 to 135 centimeters
Lowerwell settled

Past Weather

Strong south east wind and precipitation in the form of snowfall between 30 cm to 50 cm with temperatures and freezing level between 800 and 1200 meters. Thursday temperatures cooled with very little precipitation forming a breakable crust on all aspect and all elevations.

Weather Forecast

A deepening and strong low pressure will bring strong south south west wind, moderate to heavy snowfall and rising freezing levels and temperatures.

Friday 20 to 40 cm of snowfall 10 to 20 mm of rainfall. Temperatures 1 overnight rising to 6 mid day, winds moderate to strong south west . Freezing level rising to 1200 m mid day.

Saturday 5 to 10 cm of snowfall 5 to 25 mm of rainfall. Temperatures 1 overnight rising to 5 mid day, winds moderate south west. Freezing level rising to 1000 m mid day.

Sunday 5 to 10 cm of snowfall temperatures rising to 5 mid day, winds light north east. Freezing level rising to 1200 m mid day.

Posted on Friday April 13, 2018 by Jesse Percival

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