Wayne Flann Avalanche Blog: January 12, 2021

YESTERDAY:

Monday January 11, 2021. Sunrise was at 08:08 Hrs. -2 with a 20-40 KPH SE wind.

Snow gone from the trees in the valley.

Snow line was at around 1000 meters.

Whistler was just North of the atmospheric river event.

Clear to the North West.

There was some good skiing to be had on North facing slopes.

And fun air to be had.

Monday Jan 11, 2021. 15:00 Hrs. -2 with a 15-25 KPH ESE wind. +3 in the valley.

GOES image from Monday afternoon.

Good turns to be had near and in the trees.

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

2240 meters -3, Winds were 95-115 KPH SE--Horstman Hut

2180 meters -2, Winds were 70-95 KPH SE--Whistler Peak
1860 meters -1, Winds were 30-50 KPH S --Rendezvous

1835 meters -1, Winds were 20-40 KPH ESE--Round House

1650 meters 0, 12 cm in 12 Hrs, 22 cm in 24 Hrs, Base 255 cm --Pig Alley
1570 meters -2, 10 cm in 12 Hrs, 20 cm in 24 Hrs, Base 169 cm--Catskinner

660 meters 0, Valley Temp, Max temp Yesterday was +4.3, 8.6 mm of precip yesterday.

As of 07:00 Hrs this am we have obscured skies, limited visibility and its snowing 1 cm per hr.

FORECAST:

Frontal band will bring periods of light to moderate precip and strong wind in a South Westerly flow aloft. Some models have the FL rising to 2000 meters. Some 1600 meters. There is warm air aloft already. The atmospheric river event went South yesterday just brushing the area, we might have a repeat today. The front should pass by Wednesday morning with a ridge building Wednesday afternoon. Unsettled in the morning with sunny weather in the afternoon. Thursday will see some clouds move in with a mix of sun and cloud. Guesstimates: 30-45 cm above 1800 meters by Wednesday am, 0-trace by Thursday am, 2-4 cm by Friday am.

GOES IR image from this am.

Some warm air being pulled in from the South, warm front arriving with trailing cold front.

Ridge builds in by Wednesday afternoon.

Unsettled Thursday with a mix of sun and cloud.

AVALANCHE ACTIVITY:

Sz 1 from snowmobile cliff drop. 1650 m on Rainbow yesterday. Toby Salin image.

Two ski tourers injured on Republican Mountain, Montana. Article below. GNFAC Image

AC on Blackcomb yesterday produced Sz 1-1.5 Xe Sc. Sz 2 result from cornice drop.

AC on Whistler yesterday produced ssl up to Sz 1.5 Xe Xc Xl Sc. A Sz 2 Cs. Sz 1.5 Sa.

Taken from Sea to Sky Avalanche Advisory:

Avalanche Summary

On Monday reports from avalanche control using explosives saw up to size 2 slab avalanches on slopes below cornice failures.

Natural avalanche activity is expected on Tuesday during the storm. The snowpack is complex right now and it's a good time to wait out the storm before venturing into avalanche terrain.

A large (size 3) avalanche was remotely triggered by skiers on Cowboy Ridge near Whistler on Saturday. The avalanche occurred on a north to northwest aspect at around 1900 m. The crown ranged reached up to 200 cm and was approximately 200 m wide. Check out this MIN for photos and more information. A similar avalanche was remotely triggered by skiers on a nearby westerly slope on Thursday; check out this MIN for more info and photos.

These avalanches are clear evidence that the weak layers described in the Snowpack Summary are still triggerable by riders and the consequence of being caught would be high.

Otherwise, small storm and wind slab avalanches were triggered by riders and naturally on Saturday and Sunday, generally 10 to 30 cm deep, on north to northwest aspects, and at treeline and alpine elevations.

Snowpack Summary

New and reactive storm and wind slabs will continue to build Tuesday. The storm is expected to drop around 15 cm Monday night and another 20-30 cm Tuesday. The storm will come with strong southwest wind so wind slabs are expected at higher elevations. Treeline and below treeline elevations may see a loose wet avalanche cycle where the precipitation falls as rain.

The snowpack is currently quite complex. Numerous layers of surface hoar may be found in sheltered terrain in the top 100 to 150 cm. The area of greatest concern is around 100 to 200 cm deep, where surface hoar or sugary faceted grains may sit above a hard melt-freeze crust from early December. There have been several recent large natural and human-triggered avalanches on this layer, particularly around Whistler and Pemberton.

Near the base of the snowpack there may be faceted grains above a crust from early-November, which was identified as the failure layer in recent sporadic large avalanche releases.

INFORMATION & OBSERVATIONS: