Monday January 11, 2021

Wednesday January 13, 2021
Tuesday January 12, 2021
Monday January 11, 2021
Confidence: Moderate - Increase in field observations and professional reporting, Increased MIN reports providing a range of good recreational information, much appreciated, please keep them coming.

Main Concerns

Loose Wet, Persistent Slab, Wind Slab, Storm Slab - view Avalanche Problems for detailed information.

Travel & Terrain Advice

Please respect the avalanche/patrol team and workforce at Mount Washington, at no time is uphill travel or unsanctioned use of the private property permitted. We are lucky to have one of the least busy provincial parks in British Columbia and yes it may be a little more work than walking up a ski area run, its well worth the effort!

Be cognizant of snow conditions and utilize small slopes to test and investigate the recent storm snow and its reactionary properties.

Monitor changing snow conditions as new storm snow will rapidly consolidate and present slab properties as temperatures rise.

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. A small loose wet avalanche will entrain and gain enough mass to push a mountain traveler into gullies and over cliffs.

Avalanche Summary

No reports or observations of natural or human trigger avalanches over the past forecast period.

Small sloughing and some small slabs where present when ski cutting on very small features.

On Saturday, the Mount Washington Avalanche control teams reported explosives triggering a size 2.5 slab avalanche when blasting a cornice on the peak above the north bowl. Of note this large test did not step down to the PWL.

Avalanche Problems

Loose Wet

Warming temperature and precipitation in the form of rain will rapidly decrease the stability of the upper snowpack.

Location: Widespread on all aspects Tree line and below. Short periods of high freezing levels may affect the Alpine.

Possibility of triggering: During warming and rain events it is very likely to certain that like triggers such as a skier will trigger this problem and natural triggered avalanches are 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.

Persistent Slab

A layer of facets 20cm thick can be found down nearly a meter in the snowpack. Currently isolated testing of this layer is not producing results. This persistent layer is a concern because when it is trigger consequences will be severe. The likelihood may be low and its is likely that it is currently unreactive and becoming dormant. The continual loading of the snowpack with the coming forecast storms is likely to increase the magnitude and perhaps reach a tipping point where sensitivity to triggering increases.

Location: Isolated sheltered large terrain features but found on all aspects in both the Alpine and at Tree line.

Possibility of triggering: Unlikely to Possible to both natural and human triggers.

Size: If triggered expect these avalanche to be large to very large size 2 to 3

Wind Slab

Found on predominantly North aspects, this avalanche problem is likely to persist as wind transport was observed and ongoing winds will continue to load a variety of surfaces that include below 1500 meters a crust and above this elevation old storm snow. Of note the past strong South East winds prevailed and persisted, it is likely that North West thru to West aspects may have seen additional wind slab development.

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 likely to very likely from light loads such as skiers. Natural avalanches are possible to likely.

Size: If triggered expect these avalanches to be small, and on specific terrain features large size 2 and isolated features very large size 3.

Storm Slab

New storm slabs will form and be present on terrain that is not exposed to the wind, below 1500 meters wet slabs will occur during periods of rain. Expect the slab sensitivity to triggering and propagation properties to increase as temperatures increase.

Location: All aspects and elevations specific to terrain sheltered from the wind.

Possibility: Triggering of this avalanche problem is likely to very likely from light loads such as skiers. Natural avalanches are possible to likely.

Size: If triggered expect storm slab avalanches on specific terrain features to be large, size 2 and on isolated features very large size 3.

Snowpack Summary

Over the weekend intermittent moderate snowfall and intense wind transport was observed as a storm system delivered significant quantities of snow. Strong winds from the South East where recorded. The fact that the South east wind has been so intense will likely create significant loading on North West thru to West aspects, pay particularly close attention to this aspect as it will likely have very touchy wind slabs. Evidence of Intense wind transport of snow to North aspects is at all elevations.

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.

Snowpack Details

SurfaceWind affected snow, scoured on exposed South aspects with deep loading on North aspects.
UpperStorm snow and wind slabs from past storms can be found over a crust below 1500 m and over old storm snow above 1500 m.
MidA 20cm layer of facets can be found down 100cm plus.
LowerWell settled and dense.

Past Weather

The past forecast period was a mixed bag of precipitation, wind effect and short periods of warming up to 1200 meters. At elevations 1200 meters and below the upper snowpack was becoming moist dense and settling. Remote telemetry and manual weather stations report approx. 20- 30mm of precipitation fell with the west side of the island seeing 40mm. Wind speeds where moderate to strong from both the South East and South West.

Weather Forecast

A strong Northwesterly flow will continue over this next forecast period, delivering strong south west winds and precipitation. Freezing levels are expected to climb both Tuesday and Wednesday and precipitation in both the form of rain and snow are dependent on the freezing level. Initially the freezing levels will present as high when a storm front approaches, in the wake of the storm, cooling temps and dropping freezing levels will occur .

Monday: 15-30 cm, Winds Strong from the South West, Freezing levels a high of 1500 meters.

Tuesday: 15- 30 cm, Winds Strong from the South West, Freezing levels 1000 meters.

Wednesday: 10-15 cm, Winds Strong from the South West, Freezing levels a high of 1700 meters.

Posted on Monday January 11, 2021 by Jesse Percival

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