Wednesday January 13, 2021
Loose Wet, Persistent Slab, Wind Slab
Travel & Terrain Advice
Your island bulletin continues to grow, with all the information sharing and increased traffic in the backcountry, it was time. Please review out latest Instagram and Facebook post to review the extensions to your island avalanche bulletin forecast areas. We have expanded our Northern boundary to Nimpkish lake reaching to both the West and Eastern edges of the island. On the South end we reached down to Lake Cowichan and captured everything in between including 5040 peak, Mount Arrowsmith, Forbidden Plateau, the Beaufort range to name a few.
Be cognizant of snow conditions and utilize small slopes to test and investigate the recent storm snow and its reactionary properties.
Careful and cautious route finding when transitioning from scoured areas into areas of wind loaded snow.
Avoid traveling below and above cornice features as they are large and touchy.
Avoid open and steep slopes during periods of warming and rain; even small loose wet avalanches will have enough mass to push a mountain traveler into gullies and over cliffs.
On Saturday a natural avalanche of unknown size (give the terrain scale it was possibly a size 2) was witnessed occurring on a very steep North aspect slope above foster lake. Additionally in that area, other debris piles from previously natural avalanches where observed.
On Monday Mt Washington Avalanche control teams reported a few large (size 2) and numerous small (size 1) natural avalanches that had occurred on North, West and East aspects. Explosive avalanche control triggered produced a few large avalanches and numerous small soft slab avalanches. Explosive triggered avalanches where reported to easily propagate with some of the slab depths up to 100cm.
Friday afternoon warming temperatures are forecast. This will rapidly decrease the stability of the upper snowpack. Temperatures are forecast to begin cooling and this instability may be brief.
Location: Widespread on all aspects and at all elevations.
Possibility of triggering: During warming it is possible to likely that human will trigger this problem and natural avalanches are possible to likely.
Size: If triggered expect these avalanche to be small but will entrain and could become large up to size 2 with enough mass to bury injure or kill a mountain traveler.
A layer of facets 20cm thick can be found down a meter to two meters in the snowpack. Currently isolated testing of this layer is not producing results. This persistent layer is present however is likely becoming dormant as its depth and the bridging effect from a deepening snowpack is making the possibility of triggering very unlikely.
Location: Isolated sheltered large terrain features but found on all aspects in both the Alpine and at Tree line.
Possibility of triggering: Very Unlikely to both natural and human triggers.
Size: If triggered expect these avalanche to be large to very large size 2 to 3.
Found on predominantly North aspects, this avalanche problem overlies a variety of surfaces that include below 1500 meters a crust and above this elevation old storm snow. Expect that this problem will still exist, but is beginning to settle and bond with forecast cooling temperatures.
Location: North aspects and found in both the Alpine and at Tree line specific to terrain just below ridge top.
Possibility: Triggering of this avalanche problem is possible to likely from light loads such as skiers. Natural avalanches are unlikely.
Size: If triggered expect these avalanches to be small, and on isolated terrain features large, size 2.
Over the past forecast period intermittent moderate to heavy snowfall snowfall and intense wind transport was observed. A storm system delivered significant quantities of snow up to 90mm of precipitation on the west side of the island with moderate to strong winds from the South West. Evidence of intense wind transport of snow to North aspects was observed in both the Alpine and Treeline.
Overall snowpack depths have been measured from 200cm to 400cm.
A variety of crusts exist in the upper snowpack. Numerous snowpack tests indicate that these crusts are now beginning to bond to the storm snow.
The mid snowpack has an unreactive 20cm layer of facets that can be found down 100cm plus. This layer may be isolated to areas that are sheltered and at higher elevations above 1400 meters presents as a melt freeze crust/ poly grain layer.
The lower snowpack is dense and very well settled as many reports from island backcountry users and numerous snow profiles have indicated.
|Surface||Wind affected snow scoured on exposed South aspects with deep loading on North aspects. Solar aspects becoming moist 1400 meters and below.|
|Upper||Storm snow and wind slabs from past storms can be found over a crust below 1500 m and over old storm snow above 1500 m.|
|Mid||A 20cm layer of facets can be found down 100cm plus.|
|Lower||Well settled and dense.|
Past precipitation amounts topped out at 90 mm on the west side of the island with snowfall amounts nearing 45cm on the eastern side. The winds continued moderate from the south west and temps began to rise on Tuesday. Brief periods of clearing and sun presented as well causing surfaces to become moist.
A ridge of high pressure to the east of the region is expected to provide a period of cooling and clearing for both Wednesday and Thursday. Beginning late Thursday night a subtropical wave of warm air and moisture, will drive freezing levels to mountain tops 2000 meters and deliver light amounts of precipitation in the form of rain.
Wednesday: 5-10cm cm, Winds Strong easing to Moderate from the South West, Freezing levels a high of 700 meters.
Thursday: Trace amounts, Winds Moderate from the South East, Freezing levels a high of 1000 meters.
Friday: 5-10 mm, Winds Strong from the South West, Freezing levels a high of 2100 meters falling to 1200 meters.
Posted on Wednesday January 13, 2021 by Jesse Percival