Wednesday February 28, 2018
Wind Slab, Storm Slab
Travel & Terrain Advice
Wednesday’s storm will come with significant new snowfall and strong to very strong winds from the SE. Travel in the alpine is not recommended during this forecast period and extra caution, very good route finding and conservative decision making will be key to safe treeline travel. Avoid wind loaded aspects lee to the SE like large bowls, gullies, open areas and cross loaded features. N-W zones near ridge line will be very dangerous as the past winds stripped them down to the Valentines day crust. The bond of the new snow to this exposed crust will be very low. I know we are all powder hungry, but give the storm snow sometime to settle out. With strong winds the best skiing will be in the protected trees anyways. Heck its Dr Seuss’ birthday on March 2nd, so stick to the Truffala trees. “And no one has skied such trees as good as these….”
No new avalanche activity has been reported in the past two days.
Wednesday’s storm will also come with strong to very strong SE winds. These winds will significantly transport snow to lee N-W aspects in the alpine, treeline and open below treeline zones. The wind slabs created will very likely trigger naturally and are almost certain to trigger with human activity. We can expect to see avalanches up to size 2 in specific areas and up to size 3 in some isolated spots.
Significant snow fall Wednesday will load all aspects and elevations (especially alpine and treeline) creating storm slab avalanche potential. These slabs will likely trigger naturally and are very likely to trigger with human activity up to size 2.
Storm snow (20-50 cm) from last week has slowly gained strength and is now bonding well to the Valentines day crust. Approx 10-30 cm of low density sits over 10-20 cm of moderate density bonding well to the crust. Moderate winds from the N-W have stripped the storm snow from ridge line features exposing the crust, leading to some nasty skiing near summits. These winds have also created some small stubborn wind slabs in the alpine and treeline on S-E aspects and on cross loaded features. Some direct solar below treeline locations have warmed during the past two days and the snow surface became heavy and moist (potentially frozen crust in the evenings and mornings).
|Surface||variable. See above|
|Upper||20-50cm of well settled storm snow from last week, with a good bond to the Valentines day crust.|
Little to no new snow for the forecast region over the past two days. Moderate N-W winds have produced moderate transport of snow to S-E aspects. Temps have remained cool in the alpine but treeline and below treeline temps have hit zero and even a few direct solar below treeline locations hit into the positive for the first time in a long time.
Big storm system will hit the island during the day Wednesday! Light snowfall for the rest of the period, cool and mainly cloudy.
Wednesday - 20-30 cm of new snow, strong to very strong winds from the SE, temps -3 to -6, freezing levels 500-800 m.
Thursday - 3-5 cm of new snow, moderate winds from the SE, temps -4 to -7, freezing levels 0-800 m.
Friday - 0-2 cm of new snow, moderate to light winds variable, temps -3 to -7, freezing levels 0-1000 m.
Posted on Wednesday February 28, 2018 by Bill Phipps