Wayne Flann Avalanche Blog: February 12, 2021

YESTERDAY:

Thursday sunrise was at 07:29 Hrs. -19 with a 10-30 KPH East wind.

Snow guns were making quality snow. More sublimation yesterday than on Wednesday.

It was a cold morning.

High cirrus clouds to the South.

Marine clouds over the Pacific.

Blowing snow on the cord.

Thursday Feb 11, 2021. 15:00 Hrs. -21 with a 5-15 KPH NNE wind. -10 in the valley.

Groomers were fun!!

Last runs of the day.

Before sunset Wednesday evening.

Thursday sunset was at 17:23 Hrs. -20 with a 25-55 KPH ENE Wind at 2240 m..

Weather Observations for February 12, 2021 taken at 06:00 Hours.

2240 meters -19, Winds were 20-40 KPH ENE-Horstman Hut

2180 meters -22, Winds were 5-10 KPH E--Whistler Peak
1860 meters -23, Winds were 5-10 KPH SE --Rendezvous

1835 meters -23, Winds were 5-10 KPH ENE--Round House

1650 meters -23, 0 cm in 12 Hrs, trace in 24 Hrs, Base 243 cm --Pig Alley
1570 meters -23, Trace in 12 Hrs, trace in 24 Hrs, Base 175 cm--Catskinner

660 meters -17, Valley Temp, Max temp Yesterday was - 10.7, 0.0 mm of precip yesterday.

Wind chill at 2240 m this am with a 30 KPH wind= -31

Wind chill at 2180 m this am with a 15 KPH wind= -32

Wind chill at 1860 m this am with a 10 KPH wind= -31

As of 07:00 Hrs this am we have clear skies and unlimited visibility.

FORECAST:

Unsettled weather for today with a mix of sun and cloud in a Northerly flow aloft. The Arctic front remains strong and looks to deflect any incoming lows to our South. More sun than cloud this am but most of the moisture will stay along Vancouver Islands coast. Saturday will hopefully bring some snow as the low moves down the coast. Expecting periods of light snowfall early Saturday morning into Saturday afternoon. A break Saturday night with overcast skies and moderating temperatures. Periods of light snow again by Sunday afternoon into Monday. Arctic front loses ground and we should see some decent snowfall by Monday.? Unsettled by Tuesday with seasonable weather. Guesstimates: 2-6 cm by Saturday am, 2-5 cm by Sunday am, 2-6 cm by Monday am. Could get a little less or a little more depending on how the Arctic front reacts to the incoming low.

GOES IR image from this am.

Arctic front still very strong, low deflected South but fingers crossed for some snow!!

Northerly flow aloft.

500 MB image fro today.

Arctic front slowly retreating to the East, will see cloud and some light snow for Saturday.

Low to the North should have some impact in pushing the Arctic Front where it belongs.

Overcast and dry Sunday morning, should see some light snow by the afternoon.

AVALANCHE ACTIVITY:

Sa Sz 1.5 Stiff Slab NW aspect Decker Main on Thursday. Skier sustained knee injury.

Two backcountry skiers had to be rescued by military helicopter near Spire Peak. Article below.

Widespread natural cycle. Lakeside sign line was closed during the day, active Sz 1 Na cycle.

. Na Sz 1 Lakeside. Wind slab.

Above Road Runner Traverse.

Triplex Area.

Many small wind slabs, natural cycle Thursday.

Sz 2 Poop Chutes.

Na Sz 1.5-2 off the Poop Chutes.

Sz 1-2 Na's on Armchair.

On Whistler there were Pockets of 1F windslab. Some on reverse loaded slopes.

AVALANCHE SUMMARY FOR SEA TO SKY AREA:

Avalanche Summary

With cold temperatures gradually robbing the upper snowpack of cohesion, observations from the past few days show a trend away from wind slab releases and toward small loose dry avalanches triggering in steep start zones with skier traffic. That said, a few more small wind slabs were still able to be triggered with ski cutting in the Whistler area on Tuesday.

Notably, a size 3 (very large) persistent slab was remotely triggered (from a distance) by a group of skiers in the McGillivray Pass area (northern South Coast Inland region) on Monday. This occurred on a southwest aspect at 2400 metres. It was described as a hard wind slab formed over the facet layer from late January detailed in our snowpack discussion.

Snowpack Summary

Up to 15 cm of low density snow can be found on the surface in shaded, sheltered areas. In more wind exposed areas this is replaced with a mix of wind-affected surfaces, including wind slabs that are gradually losing cohesion and reactivity under prolonged cold temperatures. A thin recent sun crust may be found right near the surface on solar aspects.

Below this mixed bag of surface conditions, 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 a bit 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: