Monday March 1, 2021

Wednesday March 3, 2021
Tuesday March 2, 2021
Monday March 1, 2021
Confidence: Moderate - Few reports from the field/public. If more reports come in we will try and update the bulletin. Weather models in agreement. Warm/moist trend ending and cold temps on the way to tighten the upper snowpack.

Main Concerns

Cornice Fall, Wind Slab, Storm Slab - view Avalanche Problems for detailed information.

Travel & Terrain Advice

Continue to avoid wind loaded terrain in the alpine and treeline. Moderate amounts of new snow and strong winds, during this forecast period, will only add to the windslabs that developed previously.

Moderate amounts of new snowfall Monday and Wednesday will load on a hard sliding surface (old crust) in previously wind stripped zones. Take the time to dig down and check what the new snow is lying on and how well it is or is not bonding to the layer below.

Give cornices a wide berth as winds of late will certainly have expanded their size. Avoid travel above and below these ridge top features..

Avalanche Summary

No new avalanche activity from Mt Washington patrol

Reports of ski accidental and natural triggered avalanche activity, possibly up to size 2 from Mt Cain’s west bowl. All second hand info at this time. Hopefully the parties that experienced these can send us some more info.

Widespread pinwheeling (ie very small loose wet avalanches) have been reported at below treeline elevations island wide.

Avalanche Problems

Cornice Fall

Continued winds and new snow available for transport have feed the cornice that sit on the ridgetops. Like gargoyles these overhanging features are now at a size that they present a potential avalanche threat.

Location: alpine and treeline ridgetops on NE to NW aspects

Likelihood of triggering: Possible with natural or human triggering.

Size: 1 to 3

Wind Slab

New snowfall and strong winds forecast will either add to existing windslabs or create new slabs.

Location: NE to NW aspects in the alpine and treeline elevation bands.

Likelihood of triggering: Likely with human activity and possible with natural triggers.

Size: 1-2.5

Storm Slab

Moderate amounts of new snow ,forecast to fall this period, will land on either preexisting wind slabs or on a crust from previous weather events. Where the new snow lands on the crust, it will have a poor bond and this may result in storm slab avalanche activity.

Location: All aspects and elevations.

Likelihood of triggering: Likely with human activity and possible with natural triggering.

Size: 1-2

Snowpack Summary

The alpine and open spaces at treeline have been beaten by the winds over the past few days. Moist snow (due to warm temps and some light rain Sunday) at treeline and below treeline elevations are now cooling to a thin crust.

Snowpack Details

SurfaceWind blown snow up high. Moist snow now freezing to a new exposed crust at lower elevations
UpperAn old crust with a moderate bond to the snow above it. Some preserved dry snow under the crust.
MidWell settled with a dormant persistent weak layer and old crusts
LowerWell settled

Past Weather

Little snow has fallen over the weekend. (Mt Cain got the most with 14 cm, Strathcona Park 7 cm, Mt Washington 2 cm, and the southern reaches at around 10 cm. Strong winds have continued to move this snow around to create variable depths depending on your location. Temps climbed as the freezing levels went up to approx 1300-1500 m on Sunday and then cooled as the evening chill set in. Some light rain was reported at lower elevations Sunday.

Weather Forecast

Moderate amounts of new snow are forecast to fall with most expected Monday and Wednesday. Strong winds from SE to SW will move the new snow around. Temps will drop after the warmth of Sunday, cooling the upper snowpack.

Monday: 10 to 20 cm of new snow. Winds strong south to moderate west and south west. Temps -1 dropping to -6. freezing levels 1300 dropping to 600 m.

Tuesday: 3 to 9 cm of new snow. Winds moderate south to south west. Temps -8 to -4. Freezing levels 200 to 800 m.

Wednesday: 25 to 2 cm. Winds strong south east to moderate south east. Temps -5 to -1. Freezing levels 400 to 900 m.

Posted on Monday March 1, 2021 by Bill Phipps

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