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This Bulletin Valid Until: Friday April 14, 2017 @ 6 pm.
Confidence: Moderate- uncertain of forecast precipitation amounts
Main Concerns: (Avalanche problems)
Wind Slab- Forecast strong south east wind and new snow will form wind slab in both the alpine and treeline. These wind slabs will initially be very touchy to light triggering but over a short period of time will begin to settle and bond due to moderate air temperatures. At higher elevations expect in isolated areas these wind slabs to remain active during this forecast period. Wind slabs will be found on lee aspects (North west thru to North east) and located in terrain features such as at the base of steep cliffs, below any cornice features, ridge top areas and steep convex rolls. Avalanches from wind slabs could be large (size 2) and will be touchy to very touchy to light human triggers as snow fall amounts continue to increase and winds persist.
Cornice- Forecast new snow, wind and moderate temperatures will provide ideal conditions to form and grow cornices.These hazardous snow features can be found on ridge tops and on primarily north west thru to north east aspects and in both the alpine and at treeline.As temperatures rise and snow fall and wind is forecast to increase cornices will be fragile, unpredictable and when failing will deliver a heavy load to slopes below and may trigger in isolated terrain a much larger avalanche (size 3). Give these hazardous features a wide berth if deciding to travel either above or below them.
Travel/Terrain Advice: Dangerous avalanche conditions exist and travel in avalanche terrain during the height of the danger level during this forecast period is not recommended and should be avoided. If users choose to travel in to avalanche terrain, evaluate snow and terrain carefully and identify features and areas of concern. Plan to avoid steep open slopes and unsupported features,choose simple terrain that avoids over head hazards.
Past Weather: Over the last 72 hours, mountain weather has seen air temperatures swing from minus six to zero degrees.A total of 30 centimeters has fallen with moderate south east wind.
Avalanche Summary: Day time warming produced widespread loose sluffing and point releases of the upper surface snow on all aspects with the exception of due north. Warming has been limited and solar effect was at its strongest yesterday with a few small (size 1 to 1.5) avalanches occurring as loose point releases gained enough mass to create a few hazardous avalanches. Terrain such as rocky steep areas and steep solar aspects were most effected and overnight cooling has hardened this debris likely creating a hazard to mountain travel.
Snowpack Description The upper 60 cm of the snow pack has two significant shears that have been producing moderate resistant planar results when tested and are failing on a density change with preserved snow between two well settled slabs. The melt freeze crust buried on April fourth is as well producing moderate resistant planar results and can be found down between 60 to 80cm and possible deeper than 100cm in isolated lee aspect terrain. Past weather and solar effect and has moistened the upper snow pack and overnight cooling has formed on all aspects with the exception of due north a breakable surface crust. Below this crust a variety of both sun crust and wind crust have been observed and are dependent on orientation to both the sun and wind.
Three significant crusts exist in the upper mid snow pack with the mid February down approximately 250 cm and this being the most pronounced and supportive with facets still being found above and below this crust.The lower mid and lower snow pack continue to settle and with this settlement an increase in density and strength had been noted.
Surface- New snow has buried a well developed surface crust.
Upper- Numerous melt freeze crusts exist in the upper snow pack.
Mid- Well settled with lingering persistent weakness found between 100 and 200 cm
Lower- Well settled.
Weather Forecast: A low pressure with moderate strength will pass by the forecast region bringing with it new snow and strong south east wind. In the wake of this semi organized front, a ridge of high pressure will follow producing moderate North winds and clearing sky
Wed- up to 20 cm new snow. Winds SE to 40 km/hr.
Freezing level to 1400 m.
Thur- up to 10 cm new snow and 5mm of rain. Winds NE to 25 km/hr.
Freezing level to 1300 m.
Fri- up to 10 cm new snow Winds SE to 25 km/hr.
Freezing level to 1000 m.
Prepared by Jesse Percival