Monday January 15, 2018
Loose Wet, Wind Slab, Storm Slab
Travel & Terrain Advice
Winter version 5.0 is on its way during our season of fluctuating spring/winter conditions. Last Saturday’s rain and Sunday’s warm temps have essentially reset our snowpack, so the main thing to be wary of is where the new snow is falling and being transported to with the winds. Watch for loaded slopes and bowls and study how well the new snow is bonding to the old. Be especially cautious of route choice later in the day Wednesday with the temperature spike increasing the likelihood of triggering an avalanche in the new snow.
Saturday’s warm temps and rain created a flurry of avalanche activity on all aspects and elevations, producing numerous loose wet slides triggered both naturally and human. Those reported were fortunately in the size range of only 1-1.5, but we could expect some in the alpine were greater, if we had any alpine observations.
Warm temps and high freezing levels continue into Tuesday. Light to moderate rain will fall Monday and begin to change to snow mid Tuesday as the freezing levels finally begin to descend. These factors will therefore still mean the potential for wet loose avalanches, even thought the majority of the slopes that would produce these types of slides most likely released with the rain event last Saturday. These avalanches will be on slopes of all elevations and aspects, will be up to size 1-1.5 and may possibly trigger naturally and are likely with human activity.
Accompanied by strong south east winds, the new snow is likely to create wind slabs on north-west aspects in the alpine, treeline and open zones below treeline. These slabs could produce avalanches up to size 2-2.5 and will possibly trigger naturally and are likely to trigger with human activity. A short spike in freezing level and temperature late Wednesday afternoon into the early hours of Thursday will potentially make our slab problem more reactive to triggering as it increases the load on the new snow.
As our freezing levels and temps drop back to winter proper, precipitation will begin to fall as snow in the hills mid Tuesday. Mid Wednesday will see the brunt of this new storm system with heavy snowfall into Thursday. This new snow will potentially produce storm slabs in the alpine and on “alpine like” treeline features on all aspects up to size 2 with natural triggering possible and human triggering possible to likely.
All elevations and aspects are now moist (with solar aspects going wet during Sunday’s sun and warm temps).
|Surface||A thin new melt freeze crust has been forming overnight in the alpine and open high treeline with day time temps decomposing it.|
|Upper||Rain and warm temps have resulted in rapid settlement of the upper snowpack.|
|Mid||As temps and freezing levels begin to drop, the moist well settled upper snowpack will tighten and all but eliminate any concerns of the mid Jan, Dec and Nov crusts.|
Very high freezing levels (up towards 3000 m) accompanied light to moderate rain Saturday, right to to top of our island summits. Sunday things cleared up and brought very warm temperatures to the unseasonable range of 10 degrees on the slopes. Spring skiing conditions everywhere..
Mild temps and light rain Monday into Tuesday will ease into light snowfall. Strong south westerly flows will flush out the unseasonably warm weather, bringing us a new strong pacific storm late Wednesday into Thursday with significant snowfall. The new system will arrive with a short lived spike in temperatures and strong south east winds. Expect cloudy conditions over the forecast period so be prepaired for more difficult route finding in unknown terrain.
Mon - 8-20 mm of rain. Winds moderate from the south east. Freezing levels of 3000-1700 m
Tues - 8-14 mm of rain and 5-15 cm of snow. Winds light to strong south east. Freezing levels of 1600-500 m
Wed - 30-50 cm of snow and 10-20 mm of rain. Winds moderate to strong south east. Freezing levels of 700-1500 m
Posted on Wednesday January 17, 2018 by Bill Phipps