Wayne Flann Avalanche Blog: February 17, 2021

YESTERDAY:

Sunrise was at 07:22 Hrs on Tuesday. -7 at 1860 m with 0-5 KPH S breeze.

Low level cloud in the am.

Moist fog layer evident in some of the valleys, similar conditions to Monday.

Monday's tracks.

Stratus layer in the valley, slowly lifted, should dissipate by Wednesday.

Still soft and fun snow, with a wide spread brittle crust 2-4 cm deep from Mondays sun and moist fog.

Nice sunny breaks in the early afternoon.

Certainly unsettled.

Tuesday February 16, 2021. 14:30 Hrs. -6 with a 10-30 KPH SSW wind. +2 in the valley.

Satellite image Tuesday afternoon. Looking high and dry!

Getting nicer later in the afternoon.

Carving up the groomers.

Weather Observations for February 17, 2021 taken at 06:00 Hours.

2240 meters -12, Winds were 40-65 KPH NNE--Horstman Hut

2180 meters -11, Winds were 20-35 KPH N--Whistler Peak
1860 meters -9, Winds were 30-40 KPH N --Rendezvous

1835 meters -10, Winds were 5-50 KPH N--Round House

1650 meters - 9, 1 cm in 12 Hrs, 1 cm in 24 Hrs, Base 242 cm --Pig Alley
1570 meters -7, 1 cm in 12 Hrs, 1 cm in 24 Hrs, Base 179 cm--Catskinner

660 meters -5, Valley Temp, Max temp Yesterday was +3.1, 1.5 mm of precip yesterday.

As of 07:00 Hrs this am we have broken cloud and unlimited visibility.

FORECAST:

Brief ridging for this am in a Northerly flow aloft. The FL may rise to around 800 meters today dropping down to surface by tonight. Sunny skies will give way to some cloud later in the afternoon. Front arrives Thursday morning with periods of light snow. Another weak front arrives Friday morning with periods of light snow. More light snow for Saturday before a potent West Coast storm arrives for Sunday with wet warm windy weather. As of now it looks like the FL will stay below 1500 meters for Sundays event. Guesstimates: trace-1 cm by Thursday morning, 5-10 cm by Friday am, 5-10 cm by Saturday am, 10-15 cm by Sunday am, 30-50 cm by Monday am. Models are not in agreement with this much snow, time will tell.

GOES IR image from this am.

High pressure for the morning into the afternoon. Cloud moves in later today.

Northerly flow aloft.

Front arrives for Thursday.

Another weak front for Friday. Seasonal temps.

Looking like some precip on Friday.

AVALANCHE ACTIVITY:

Some loose dry activity yesterday.

Sz 1 Loose Dry.

Recent fracture lines in Way Poopy.

Finally a decent picture taking day, Fatal avalanche from Friday Feb 12, 2021. Poop Chutes

Point releases on Tuesday in steep terrain.

Fresh track Tuesday, fresh wind slab release from Monday evening..

Avalanche from Friday that fractured persons pelvis when trundled over the moraine.

Old debris beside S Turn.

New point releases and Monday's activity.

Avalanche mitigation on Whistler yesterday produced 1 Sz 2 Xc and some Sz 1 soft slabs Sc.

From the Sea to Sky Bulletin:

Avalanche Summary

Recent outflow winds created a widespread and reactive windslab problem that continued to produce avalanches on Monday. A size 2 persistent avalanche was triggered by a skier on the west side of Blackcomb Peak, the crown ranged from 5-90 cm and failed on facets. A size 1.5 windslab was remote triggered on the northwest face of Oboe. Additionally, numerous dry-loose avalanches were observed up to size 2, many running far and entraining large amounts of snow. Wet-loose avalanches failed naturally and were reactive to skiers Monday afternoon.

Sunday was a much quieter day for avalanche activity. Avalanche control work produced very small avalanches with the exception being a single size 2.

A fatal avalanche occurred in the region on Saturday in the Brandywine valley. The person caught was carried several hundred metres over steep, rugged terrain and through treed slopes below. The avalanche is described as a size 1 (small) wind slab on a southwest aspect at 1700 metres. The incident report can be seen here.

On Friday, a large (size 2.5), fatal avalanche was triggered by skiers at 2200 metres on a west-facing slope on Phalanx Mountain. The avalanche is described as a wind slab that formed to the lee of recent strong east winds. Two people out of a group of three were involved in the avalanche and one person was killed. The incident report can be seen here. A second, smaller (size 1.5) wind slab was triggered by skiers on a nearby slope, again causing injury to the person involved.

A bout of strong northerly winds on Thursday caused conditions in the region to change rapidly, with new and touchy wind slabs forming in unusual places. Numerous natural releases from size 1 to size 2 were observed in the Whistler area above about 1900 metres on and since Thursday.

It is important to note wind has not affected elevation bands uniformly across the region, with heavy wind effect and slab formation noted even below treeline in some areas. This is a critical piece of information as new snow obscures existing wind slab formations.

Two more skiers were involved in an avalanche in the Supercouloir feature of Mamquam Mountain on Thursday. This avalanche was a natural wind slab release and again resulted in serious injuries and an urgent evacuation by helicopter.

Snowpack Summary

10-30 cm low density snow overlies a variety of wind affected surfaces and facets in the alpine and into treeline. Isolated windslabs remain reactive from recent outflow winds. New, thin windslabs have formed in lee terrain. A thin melt-freeze crust has developed on solar aspects.

Below the evolving surface, 50-100 cm of settled storm snow sits on a persistent weak layer from late January that consists of facets at upper elevations, surface hoar in sheltered areas, a melt-freeze crust below 1900 m, and a sun crust on south-facing slopes. There could be more than 100 cm on this layer in wind loaded areas. Although this structure is suspect, we have no recent reports of avalanches failing at this interface within the region.

A crust from early December, currently considered dormant, may be found around 200+ cm deep in the snowpack.

INFORMATION & OBSERVATIONS:

1-2 cm brittle crust on solar aspects. There is a temperature crust on other aspects. Buried 2-5 cm.