Wayne Flann Avalanche Blog: February 5, 2021

YESTERDAY:

Thursday sunrise was at 07:41 Hrs. -6 with a 5-15 KPH NNE wind. 0 Deg C in the valley.

Each area has its challenges.

Thick upper and mid cloud layers with fog just above the valley floor.

Frosty in the alpine.

Nice grooming but challenging visibility. Use the force!!

A brief break in the am.

There was some decent visibility at times in the alpine yesterday.

Thursday Feb 4, 2021. 14:00 Hrs. -4 with a 15-35 KPH SW wind. +1 in the valley.

Rex Block pattern in the Pacific.

Below the clouds in the afternoon. Started snowing later in the afternoon.

Weather Observations for February 5, 2021 taken at 06:00 Hours.

2240 meters -7, Winds were 40-50 KPH N--Horstman Hut

2180 meters -7, Winds were 20-35 KPH NNE--Whistler Peak
1860 meters -5, Winds were 15-20 KPH NNE --Rendezvous

1835 meters -5, Winds were 5-10 KPH WSW--Round House

1650 meters -5, trace in 12 Hrs, 2 cm in 24 Hrs, Base 255 cm --Pig Alley
1570 meters -4, 2 cm in 12 Hrs, 3 cm in 24 Hrs, Base 188 cm--Catskinner

660 meters 0, Valley Temp, Max temp Yesterday was +1.5, 3.2 mm of precip yesterday.

There were 80-100 KPH West winds last night at 2180 meters.

Affected the Pig Alley weather plot.

Dress on the warm side, -7 with a 30 KPH North wind brings wind chill to -16. If your heading up into the alpine early.

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

FORECAST:

Ridging for today with mostly sunny skies and some cloud in a North West flow aloft. The FL might get up to around 1200 meters, dropping back down to 800 tonight. The next warm frontal band will bring an impulse of precip on Saturday with steady light precip and the FL hovering in the 800-1000 meter range. The trough of low pressure will bring periods of light precip on Sunday with cooler temperatures influenced by the arctic front. Ridge pushes in for Monday with sunny skies and cold temperatures. Looking like dry cold weather for next week. Guesstimates: 2-5 cm by Saturday am, 15-25 cm by Sunday am, 4-8 cm by Monday am. Most models are only calling for 5 cm snow on Saturday. Time will tell!!

GOES IR image from this am.

High strengthens today with sunny skies but on the warm side.

High pressure for today with light-moderate Northerly winds.

Warm front with trailing cold front brings snow for Saturday.

Going with the ECWMF model for Saturday.

Arctic air reaches us by Sunday with flurries in the mix.

AVALANCHE ACTIVITY:

An avalanche has killed a skier on Marvins Avalanche Path East of Vail. Article below.VSP Pic

An avalanche has killed a ski tourer on Etna Summit, CA. Article below. Mt Shasta AC Pic

Avalanche mitigation on Blackcomb yesterday produced some Sz 1 Sc 1F windslabs.

Avalanche mitigation on Whistler produced some Sz 1.5 windslabs Sc. 4F-P

From Sea to Sky Avalanche Advisory:

Avalanche Summary

In the clear weather on Wednesday, evidence of a widespread natural storm slab avalanche cycle was observed. It is suspected to have occurred during the storm on Monday night.

There have been reports of numerous size 1-2 natural, human and explosives triggered avalanches every day since Saturday. Many of these avalanches have failed on the recently buried persistent weak layer. Most recently, explosive control work conducted on Wednesday produced size 2 cornice and storm slab avalanches.

Snowpack Summary

50-100 cm of recent snow sits on a persistent weak layer 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.

A crust from early December may be found around 200+ cm deep in the snowpack. In shallow rocky areas, it may still be possible to trigger this layer. In deeper snowpack areas, it appears to be unreactive.

INFORMATION & OBSERVATIONS: