Wayne Flann Avalanche Blog: February 13, 2021

YESTERDAY:

Sunrise Friday was at 07:28 Hrs. At 2240 m it was -20 with a 30-40 KPH East wind. -33 wind chill.

Some high thin cloud on Friday am.

North outflow winds in the am.

Still sublimation but awesome turns in the man made powder.

Very cold temperatures in the past few days.

Clouds were moving in from the South in the am.

Low was beginning to push in some cloud.

Pumping out snow, how much water is being used and lost factoring in sublimation?

Friday February 12, 2021. 15:00 Hrs. -18 with a 5-15 KPH North wind. -10 in the valley.

There was a lot of helicopter traffic in the pm. 2 avalanche incidents yesterday in the backcountry.

Thin cloud cover later in the afternoon.

Weather Observations for February 13, 2021 taken at 06:00 Hours.

2240 meters -11, Winds were 30-45 KPH E--Horstman Hut

2180 meters -13, Winds were 35-50 KPH E--Whistler Peak
1860 meters -16, Winds were 5-10 KPH NNE --Rendezvous

1835 meters -18, Winds were 5-15 KPH N--Round House

1650 meters -16, 1 cm in 12 Hrs, 1 cm in 24 Hrs, Base 239 cm --Pig Alley
1570 meters -16, 1 cm in 12 Hrs, 1 cm in 24 Hrs, Base 175 cm--Catskinner

660 meters -10, Valley Temp, Max temp Yesterday was -9.2, 0.0 mm of precip yesterday.

Wind chill at 2180 meters at 06:00 Hrs with a 40 KPH wind= -25.

As of 07:00 Hrs this am we have overcast skies, variable visibility and it is snowing lightly.

FORECAST:

Overcast with periods of light snow for today in a Westerly flow aloft. The FL will remain well below surface with slightly warmer temps. Light snow should diminish to flurries by the afternoon. Overcast skies for tonight with another weak impulse of moisture and unsettled conditions for Sunday. Likely see some brief breaks around noon on Valentines Day. Another weak impulse of moisture arrives early Monday morning with periods of light snow, temperatures back to normal values for this time of the year. Spotty snow for most of next week with a proper front arriving Saturday and Sunday. More on that as we get closer. Guesstimates: 1-5 cm by Sunday am, 1-5 cm by Monday am, 1-3 cm by Tuesday am, trace to 1 cm by Wednesday am.

GOES IR image from this am.

Low just off the coast, Arctic Front still pushing back, most of the moisture going South.

Westerly flow aloft.

Weak front for Sunday with some unsettled weather.

Weak impulse with some moisture for Monday. Temps returning to normal values.

. Weak low with some light precip for Monday.

AVALANCHE ACTIVITY:

Blackcomb patrol responding to an avalanche in the Poop Chutes, 1 fatality. Article below.

An avalanche has killed a ski tourer near Safiendal, Switzerland. Article below. Net Pic

Sz 1.5 Sa from Thur NW Aspect Decker. Stiff slab injured a backcountry skier. MIN report below.

Na Sz 1 out of Upper Body bag on Thursday. It was a wide spread active natural cycle.

Sz 1 from Hx Friday am - Sz 2 from Na Thursday afternoon.

Avalanche Debris from Sz 2 stiff slab out of Lakeside Bowl on Thursday afternoon.

Avalanche mitigation on Blackcomb yesterday produced little results Xh, Sz 1 in Lakeside.

Avalanche Mitigation on Whistler yest produced Ltd Sz 1 Xe stiff slabs. Loading on W & SW aspects.

AVALANCHE SUMMARY FOR SEA TO SKY AREA:

Avalanche Summary

We have preliminary information about a large (size 3) avalanche occurring in the vicinity of Blackcomb Mountain on Friday. We will update this summary once we have more details.

A bout of strong northerly winds on Thursday caused conditions in the region to change rapidly, with new and touchy wind slabs forming in many leeward terrain features. Numerous natural releases from size 1 to size 2 were observed in the Whistler area above about 1900 metres. We are awaiting further detail about a skier-triggered avalanche that occurred in the Mamquam Glacier area on Thursday.

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

Ongoing elevated winds from the east and northeast have been redistributing loose snow into reactive new wind slabs in the lee of exposed terrain features at higher elevations.

The snow surface otherwise is composed of up to 15 cm of low density snow in shaded, sheltered areas (now likely a bit more scarce), along with more widespread wind-affected surfaces, including older wind slabs that have been gradually losing cohesion and reactivity under prolonged cold temperatures. On solar aspects, a thin recent sun crust may be found on or right near the surface or beneath recently wind transported snow, potentially contributing to the reactivity of new slabs on sun-exposed aspects.

Below these variable 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 suspect, we have no recent reports of avalanches failing at this interface within the region. Details of the failure planes involved in two recent avalanches are still pending.

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

INFORMATION & OBSERVATIONS:

First light East side of Mount Currie.