Friday February 12, 2021
Persistent Slab, Wind Slab, Loose Dry
Travel & Terrain Advice
Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route-finding and conservative decision-making is essential
Avoid convex roll features.
Seek terrain that is well supported.
Caution when transitioning from areas scoured by the wind into areas with recent wind loading.
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No new avalanche observed or reported over the past forecast period.
This problem has now become stubborn to triggering.
Location: This problem is widespread, however isolated areas such as convex rolls and unsupported terrain is where it is most concerning.
Possibility: Triggering of this avalanche problem from light loads such as skiers are unlikely. Natural avalanches are very unlikely.
Size: If triggered, expect these avalanches to be large size 2.
This problem may be small but in specific terrain with larger adjacent areas of fetch it is likely to be problematic. Forecast north winds will transport new available snow. Expect this problem to become larger in terms of destructive size and increasingly sensitive to triggering as winds continue.
Location: Specific to South aspects in areas lee of ridgetops. Reverse winds expected Sunday may begin to develop new wind slab on North aspects.
Possibility: Triggering of this avalanche problem from light loads such as skiers are possible to likely. Natural avalanches are possible.
Size: If triggered, expect these avalanches to be small size 1 but in specific terrain with available fetch zones to be large up to size 2, in isolated terrain features very large up to size 3.
New low density snow will be touchy to light triggers such as skier traffic and when triggered will easily gain mass.
Possibility: Triggering of this avalanche problem from light loads such as skiers is likely to very likely. Natural avalanches are likely.
Size: If triggered, expect these avalanches to be small size 1 in specific terrain features expect large avalanches size 2
Surface hoar from size 10 to 20mm has been observed Tree line and below in specific areas protected from the wind and sun. Take time to observe and report its location as it will provide helpful information to the forecast team as future snow storms are likely to eventually bury it. Cool temps have begun to facet some of the upper surfaces and in areas are breaking down the upper surface crusts.
The Jan 23, 2021 Persistent weak layer can be found between 60 and 100 cm deep and has been reactive to past testing.
Available low density snow has been observed being transported by the north wind and small wind slabs are present on southerly terrain, expect as the scale of terrain increases that these winds slab will be exponentially bigger.
|Surface||Highly variable surface conitions, new low density snow, wind scoured at upper ridge tops and wind loaded on southerly aspects. Surface hoar is forming on isolated terrain sheltered from the wind and sun.|
|Upper||A dense and strong layer of well bonded and settled snow.|
|Mid||An eroding crust with facets at its base ( JAN 21 PWL)|
Cool temperatures and moderate to strong North winds have been transporting limited amounts of available snow . Cool temperatures and clear skies are promoting the formation of surface hoar and it is present in isolated areas sheltered and protected from both the sun and wind.
A stationary high pressure to the east of the region will continue to draw artic air into the forecast area. Beginning late Friday, weak frontal systems will begin bringing some precipitation to the area. The artic air and associated high pressure will retreat Sunday as the region will return to a typical seasonal western zonal flow. Temps and freezing levels will begin to rise.
Friday: No new snow, Winds Light to Moderate from the Northeast, Freezing levels at sea level with a day time a high of 200 meters.
Saturday: 5-10cm of snow, Winds Moderate to Strong from the North East , Freezing levels at sea level with a day time a high of 500 meters.
Sunday: 1-5cm. Winds Light to Moderate from the South East, Freezing levels at sea level with a day time a high of 500 meters.
Posted on Thursday February 11, 2021 by Jesse Percival