Friday February 2, 2018
Cornice Fall, Loose Wet, Wind Slab
Travel & Terrain Advice
Ensure awareness and use extra caution when transitioning into terrain effected by wind and where snow has been transported by wind Pay careful attention to snow conditions as freezing levels rise and temperatures warm. *Take precautions when travelling either above and below a cornice.
A past natural avalanche cycle produced numerous size two avalanches and large debris piles are still evident in run outs. On Thursday size one wind slab avalanches have been reported to be easily trigger by ski cutting on N asp terrain at TL on a convex roll. These avalanches failed on a melt-freeze crust buried on Tuesday down 10 cm.
Cornices have had the chance to form and grow over the preceding weeks and can be found on predominately north aspects at treeline and in the alpine. Expect cornice noses to become frail and are likely to be naturally failing and almost certainly trigger by human traffic during forecast rain and warming events. When triggered these large chunks of heavy snow could become a trigger for further loose wet avalanches or wind slabs and have the potential to produce size 2 avalanches or greater.
Warming temperatures will promote the upper snow pack to settle rapidly becoming sensitive to human triggering and when triggered will gain mass with ease. These avalanches will be found on all aspects and at all elevations and a likely to be triggered by human traffic . Even small avalanches will have the ability to gain enough mass to bury injure or kill a mountain traveler.
Strong to moderate south east wind has over the last few days transported snow to northern aspects. Found a treeline and in the alpine these avalanche problems with forecast warming temperatures will become progressively more sensitive to human triggers and are likely to be up-to size 2 when triggered.
Snow pack depths are approaching the 4 meter mark and have seen both rapid accumulations and large fluctuation in temperatures over the past week. On Monday warm temperatures followed by a cold snap, with freezing levels near sea level on Tuesday produced a widespread melt freeze crust found on all aspects and up-to 1600 meter elevation Over the past 48 hours this crust has been buried under 15 to 20 cm of new low density snow. Continued moderate south east winds have transported this new snow to north aspect terrain and has buried this crust up-to 20 cm deep. Mid December melt freeze crust can be found down up-to 200 cm. lower snow-pack is well settled.
|Upper||Buried rain crust|
|Mid||Well settled with mid December rain crust buried down over 200cm|
warm temperatures to near sea level freezing temperatures, followed by light to moderate snowfall.
A series of pacific storm fronts will bring to the region, rising freezing levels, moderate south west wind and moderate precipitation amounts.
Friday 5-10 mm of rain, temps 1 to 3, winds light to moderate Sw, freezing level .1500 to 2000 m
Saturday 5-10 mm of rain, temps -5 rising to +3, winds moderate Sw, freezing level 1700-2300 m.
Sunday 15-30 mm of rain, temps +3 dropping to 0, winds moderate Sw, freezing level 2600 dropping to 1500 m at days end.
Posted on Friday February 2, 2018 by Jesse Percival