Monday January 4, 2021

Wednesday January 6, 2021
Tuesday January 5, 2021
Monday January 4, 2021
Confidence: Moderate - Many days of field data but at the same time many remote weather stations failed to report.

Main Concerns

Wind Slab, Loose Dry - view Avalanche Problems for detailed information.

Travel & Terrain Advice

Avoid avalanche terrain after the snow storm Sunday night Jan 3 and during/after the large snowfall coming Tuesday during the day Jan 5.

Winds during these two snowfalls will be strong to extreme from the SE, so NW slopes will be especially dangerous due to wind loading.

Avalanche Summary

Few reports of natural triggered avalanches up to size two were sent in to the bulletin. Thankfully there have not been any reports of human triggered avalanches, so it seems folks played safely out there.

Thanks to Russell Jensen for the report and pictures of the natural slide he came across in the Beaufort range, Phil Stone for his good conditions on Mt Kitchener report, and Natasha Rafo for her Elk Mt run down with alarming snow pit data.

Avalanche Problems

Wind Slab

Both future snowfall events (Sunday Jan 3 in to Monday morning Jan 4 and the storm Tuesday Jan 5) will be accompanied by strong to extreme SE winds. These winds will transport snow to NW aspects and create wind slabs that may produce avalanches.

Locations NW aspects in the alpine and treeline elevation bands and on the lee side of cross loaded features.

Sensitivity to triggering: Likely to natural triggering and very likely to human triggering

Avalanche size: one to three

Loose Dry

New snow falling Sunday Jan 3 into Monday morning Jan 4 as well as the big snowfall Tuesday Jan 5 will potential lead to loose dry avalanches.

Location: All aspects and elevations

Sensitivity to triggering: Possible with natural activity and likely with human traffic.

Avalanche size: one to two

Snowpack Summary

On average a meter of snow has fallen since Dec 29. The majority of this new snow has fallen with warm temps so it has been moist heavy snow. From approx 1300 m down a bit of rain has mixed in with these snow events. Above 1300 m it has all been snow. Our typical island snowpack did a great job of healing well after the big storms. Conditions certainly seemed to stabilize by Sunday Jan 3 on SE to SW aspects, while the NE to NW aspects (where there was significant wind loading from Saturday Jan 2) seemed to be slower to heal and even saw natural avalanche activity.

Snowpack Details

Surface5 to 15 cm of new low density powder in sheltered areas, wind effected snow in open zones and ridgetops.
Upper1300 m and below a thin rain crust over storm snow, above 1300 m settling storm snow.
MidWell settled with some old crusts
LowerWell settled

Past Weather

50 to 100 cm of new snow has fallen in the past few days. Extreme SW to SE winds transported a significant amount of snow to NE and NW aspects and on to cross loaded features Saturday. At the tail end of Saturday’s storm a short lived bit of rain fell below 1300 m followed by clear cold skies. Sunday saw 5 to 15 cm of new snow fall early in the morning with cool temperatures and low winds.

Weather Forecast

Once again two big snow storms will hit the island this bulletin period, Sunday night Jan 3 into Monday morning Jan 4 and during the day Tuesday Jan 5. Winds will be strong to extreme during these storms, but temperatures will be on the colder side.

Monday Jan 4: 15 to 30 cm of new snow falling Sunday night into Monday morning (some of the lower mountain elevations in the southern zones may see a bit of this precip start out as rain due to a slightly higher freezing level/temp). Winds Strong to Extreme SE during the snowfall, dropping to moderate SW. Temps at 1500 m 0 to -5 for central/north island, and + 2 to -4 for south. Freezing levels 1200 dropping to 900 m for central and north, 1700 dropping to 900 m for south.

Tuesday Jan 5: 30 to 70 cm of new snow during the day. Winds extreme to strong SE. Temps at 1500 m 0 to -4. Freezing levels 800 to 900 m.

Wednesday Jan 6: 5 to 15 cm of new snow. Winds Light to moderate SW to variable. Temps at 1500 m -2 to -5. Freezing levels 1000 to 800 m.

Posted on Monday January 4, 2021 by Bill Phipps

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