Wayne Flann Avalanche Blog: December 28, 2020

YESTERDAY:

Sunrise Sunday was at 08:11 Hrs. -6 with a 10-15 KPH SE wind. 0 in the valley.

-8 as of 09:00 Hrs in the alpine.

There was some nice light in the am.

Mount Currie Sunday am.

Upper and mid layer clouds did eventually move in.

The weak front did arrive very slowly.

Sunday December 27, 2020. 14:00 Hrs. -5 with a 0-5 KPH East breeze. 0 Deg C in the valley.

Satellite image from the same Timeframe.

Just before sunset.

Weather Observations for December 28, 2020 taken at 06:00 Hours.

2240 meters -6, Winds were 10-20 KPH NNE--Horstman Hut

2180 meters -6, Winds were 10-15 KPH NNE--Whistler Peak
1860 meters -5, Winds were 0-5 KPH NNE --Rendezvous

1835 meters -5, Winds were 0-5 KPH NNE--Round House

1650 meters -5, 6 cm in 12 Hrs, 13 cm in 24 Hrs, Base 160 cm --Pig Alley
1560 meters -5, 5 cm in 12 Hrs, 11 cm in 24 Hrs, Base 100 cm--Catskinner

660 meters -1, Valley Temp, Max temp Yesterday was +3.1, 3.1 mm of precip yesterday.

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

FORECAST:

Some lingering cloud this am will dissipate as a ridge of high pressure builds into the area in a North Westerly flow aloft. The FL will rise and hover in the 900 meter range. Unsettled Tuesday am with mostly cloudy skies as the next front moves onshore. Should see light precip by late Tuesday afternoon continuing into Wednesday as another fontal band arrives. Unsettled Thursday with some periods of light snow. A potent front arrives for Friday and Saturday. Guesstimates: 0 cm by Tuesday am, 14-18 cm by Wednesday am, 2-6 cm by Thursday am.

GOES IR image from this am.

Upper level ridge builds today with mostly sunny skies.

Cloud will move in Tuesday as the ridge shifts east. Front arrives Tuesday evening.

Cold front for Wednesday with diminishing precip.

AVALANCHE ACTIVITY:

An avalanche near Berthoud Pass, CO has killed a ski tourer. Article below. CAIC Pic

Death toll from avalanches in Iran now reach 12 people. Article Below. Net Pic

One soldier dead, one missing after avalanche in Turkey. Article below. Net pic

Avalanche control on Whistler yesterday produced Sz 1-1.5 Xc, Xe. Sz 1 Na on Oboe.

Avalanche Control on Blackcomb yesterday produced some Sz 1 ssl with Sc on steep terrain.

From Sea to Sky Advisory:

Avalanche Summary

Storm slabs and cornices were reported to be touchy during the storm on Saturday, skier end explosive control work producing storm slab avalanches size 1-2.

Last week, numerous wind slab avalanches were reported, triggered naturally and by riders at treeline and alpine elevations. Check out these MINs for a few examples: here, here and here.

A few large avalanches were observed last week, running on buried weak layers (described in snowpack summary). Most occurred on north to east aspects in the alpine. A size 2.5 reported Thursday from a coastal glaciated area west of the Squamish river was on a southeast aspect, 100 m wide with crown depth 40-80 cm deep.

Snowpack Summary

15-30 cm of recent snow has been redistributed by strong south to east winds, depositing deep pockets of storm slab into lee terrain features.

Two potential concerning weak layers may be present in the snowpack:

The shallower layer, around 60 to 100 cm deep, includes feathery surface hoar crystals. This layer may be found in sheltered terrain features at treeline and lower alpine elevations but has been reported as spotty across the region.
The more widespread weak layer includes sugary faceted grains that overlies a hard melt-freeze crust. This layer ranges in depth from 10 cm to 120 cm due to the wind scouring and loading the snow in different terrain features over the past two weeks. The layer has been reported as being widespread up to around 2000 to 2200 m.

To date we have mostly seen sporadic avalanche activity on these layers, but they remain possible to trigger where they exist in the mountains.

The remainder of the snowpack is well-settled.

INFORMATION & OBSERVATIONS:

Nice dry snow Sunday am.