Friday March 23, 2018
Wind Slab, Storm Slab
Travel & Terrain Advice
More new snow will fall Friday with cold temps, which will result in a slower bonding process to that which fell on Thursday. Continue to study the bond of all the storm snow to the old crust and now this potential new snow failure/shear. We will all be stoked to get out for what might be the last powder weekend of the season (OK hopefully not the last … ), but don’t let your desires to shred and your commitment to goals mask the potential dangers that exist. The avalanches don’t know its nearing the end of the season. Use the same cautious travel techniques you would as you entered a brand new snow pack, cause that’s what we essentially have with all this new snow. Areas like west Strathcona Park have the potential to see up to 55 cm of new! Moderate, gusting to strong, SE-SW winds have transported significant quantities of snow and the wind slab danger is high! Avoid large open lee slopes (W-N-E) and cross loaded features in the alpine, treeline and even open below treeline.
Avalanche control on Mt Washington Thursday produced numerous size one wind slab avalanches with explosives and ski cutting on N-E aspects at treeline down approximately 5-20 cm.
Significant new snow with moderate gusting to strong SE-SW winds have definitely created widespread wind slabs on lee (W-N-E) slopes and on cross loaded features in the alpine, treeline and even open below treeline. These slab could possibly trigger naturally and will very likely trigger with human activity up to size 3 in the alpine, 2 at treeline and 1-1.5 below treeline.
New snow fall with potential failures on the old crust and with in the new snow itself, could create storm slab avalanches. These avalanches may be found on all aspects in the alpine and treeline and could potentially be up to size 2. They may possibly trigger naturally and will very likely trigger with human activity.
10-30 cm of new snow fell in the forecast region Thursday, luckily coming warm at first and then cooling during the event. This promoted moderate bonding to the old spring crust that we were all getting tired of playing on. Additional new snow Friday night with more forecast to fall during the day will come in cool and cold.
|Surface||new low density snow with significant wind effect in open areas at all elevations|
|Upper||warmer new snow (from Thursday) bonding moderately to the old crust.|
|Mid||moist snow, well settled cooling and becoming very stable|
Lots of new snow…. approx 12 cm in the north, 17 cm in the east and a wonderful 27 cm to the west fell Thursday giving new life to our adventures. Yeah winters back! The new snow came in moist and warm (promoting some bonding to the spring crust) and cooled as it tapered off in the afternoon. Friday night saw more moderate snow fall with cooler temps. Winds have been moderate, gusting to strong from the SE-SW and widespread wind transport was witnessed all day Thursday.
More new snow Friday during the day and the temps will remain nice and cool over the weekend. Should be great conditions for adventures as long as we play safe and avoid areas of concern.
Friday - 20 cm of new snow, winds moderate E-S, temps -4 to -6, freezing level 400 to 900 m.
Saturday - 0-10 cm of new snow, winds light from variable directions, temps -3 to -7, freezing level 200 to 1000 m.
Sunday - 2-6 cm of new snow, winds light rising to moderate SW, temps -4 to -7, freezing level 75 to 900 m.
Posted on Friday March 23, 2018 by Bill Phipps