Monday April 16, 2018

Monday April 16, 2018
Tuesday April 17, 2018
Wednesday April 18, 2018
Confidence: High - Weather models in agreement. When and where convective alpine snow showers fall remains difficult to pinpoint.

Main Concerns

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

Travel & Terrain Advice

Seek terrain options went either entering wind loaded terrain or when considering traveling over a wind effected terrain feature like a convex roll.

Avoid south aspect terrain, when daytime temperatures begin to rise and if and when the sun comes out.

Identify terrain traps and avoid as even a small loose wet avalanche will gain mass and pose a potential threat.

Provide a wide berth and increase the margin of safety when travelling either above or below cornices.

Avalanche Summary

No new natural avalanches observed and no reports of skier triggered avalanches.

If you have any information about conditions or activity in the back country or If you have observed avalanche activity or been involved in an avalanche, please send your observations to us at forecaster@islandavalanchebulletin.com.

Avalanche Problems

Cornice Fall

New snow and moderate to strong south west and south east winds have continued to contribute to already very large cornices. Found on north aspects in both the alpine and at tree line. Expect these frail hazardous features to be sensitive to human triggering and its very likely that a traveler will upon approach, trigger a cornice fall. If trigger these hazardous features could when failing and falling onto the slopes below, then trigger either a wind slab or loose wet avalanche. Expect if triggered these avalanches to be large in size and in isolated terrain very large all with the potential to bury injure or kill a mountain traveler.

Loose Wet

Daytime warming and solar effect specific to southern aspects will decompose the upper snow pack and contribute to the formation of loose wet avalanches. Expect to find these avalanches at all elevations and especially treeline and below and be very touchy to human triggering. If triggered these hazardous avalanches will initially start as small but will gain mass and become large, size 2 and in big and exposed terrain features have the ability to become very large.

Wind Slab

Past strong winds and snowfall have on northern aspects at ridge top and specific terrain features created wind slab. Expect to find these wind slabs in the alpine and at tree line and to be touchy to light triggers such as skiers or snowboarders. If triggered these avalanches will be large in size up to or exceeding size 2 and have the ability to bury injure or kill a mountain traveler.

Snowpack Summary

Strong south wind and snow fall amounts between 30 and 50 cm over the past forecast period have contributed to variable surface conditions and wind slabs have developed on lee aspects. Testing has found this newly transported snow is binding but producing moderate resistant planar results. The march 22 crust can now be found down over 145 cm and is still reactive to testing but all within the hard range. The lower snow pack is well settled and continues to strengthen.

Snowpack Details

Surfacevariable surface conditions with a breakable crust
Uppermoist and wet snow
Midmarch 22 melt freeze crust can be found down from 90 to 150 centimeters
Lowerwell settled

Past Weather

Strong south east and south west winds and moderate to at times heavy snowfall rates have deposited between 40 to 60 centimeters down as low as 800 meters. This past weather event has rebuilt the upper snow pack with various layers of moist and wet snow. Following Fridays winter like storm, daytime temperatures rose with cool nights, these factors combined with solar effect created a breakable crust on all aspects and at all elevations.

Weather Forecast

A Southern flow followed by a ridge of high pressure in the region will deflect most of the weather around the forecast area. Beginning Monday, we will see some relief from pacific weather fronts with clearing and some sun, very little precipitation and mostly light to moderate north winds.

Monday no new snowfall. Temperatures 1 overnight rising to 5 mid day, winds light south east. Freezing level 1000 m rising to 1600 m.

Tuesday no new snowfall slight possibility of rainfall. Temperatures 0 overnight rising to 4 by mid day, winds light to moderate north west. Freezing level 900 m to 1200.

Wednesday 5 to 10 cm new snowfall, temperatures 0 rising to 5 mid day, winds light to moderate south west. Freezing level 800 to 1400 m.

Posted on Monday April 16, 2018 by Jesse Percival

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