Northern San Juan
AvalancheAnonymous · Dec 31, 2019 · Northern San Juan
Weather
Clear blue bird weather, mild temperatures, no wind, no signs of snowpack surface warming from air temperature or solar radiation.
Snowpack
1-2 feet of recent snowfall from previous storms, preserved powder in the trees, lower elevations had the most well preserved and unaffected snow. As we increased in elevation along our tour we started to notice the snow was impacted by melt/freeze crust, sun, and wind.
Avalanche
On the afternoon of December 31 2019, a group of four splitboarders accessed the Black Face area from the parking lot off of Lizard Head Pass. All riders were fully equipped with the necessary avalanche gear, the plan was to have a mellow tour up to the Black Face and ski a line. The tour accessed the Black Face ridge line via the more gentle western approach up the ridge. Snow in the trees and open appeared affected by melt/freeze crusts, sun, and wind as the party gained elevation. Once on the ridge line the party traversed slightly to the east to find a more gentle slope with less of a convex rolling feature, trees, and safety zones to stop at while the riders descended. On the traverse rider 1 weighted the slopes and noticed wind affected snow on the ridge, on the traverse no signs of wumping or cracking were noticed, the snowpack appeared scoured on the ridge line and thin. All four riders transitioned to downhill mode, rider 1 ski cut the wind affected top slope of the ridge and noticed no instabilities and stopped at a safe zone. Rider 2 descended through the top wind affected slope and stopped at another safe zone below rider 1. Rider 1 then ski cut again across the slope to access better snow and skied 200-300 feet down to the trees and a relatively safe zone, rider 2 skied down to rider 1 where they radioed to rider 3 to start descending. Rider 3 rode through the second ski cut that rider 1 put in and then yelled avalanche down to riders 1 and 2. Riders 1 and 2 both made verbal statements of an incoming avalanche and quickly decided to grab on to the trees in front of them and hold on and maintain eye contact with each other in case of a ride or burial. Rider 3 broke the avalanche at the crown and stopped immediately as it began propagating and running down the slope. Riders 1 and 2 were directly in the middle of the slide path and both were buried, rider 1 was buried above his waist and rider 2 was buried to his neck, both riders maintained verbal and eye contact and immediately after the slide stopped were able to dig themselves out, and radio to riders 3 and 4 to assess the situation. At this point all riders were in contact, accounted for, no longer buried and agreed to have riders 3 and 4 ski the slide debris and regroup. All riders were uninjured and skied the slide debris out to the skin track to travel to the parking area. No other parties were observed in the area as it was late afternoon during the descent. The avalanche was a dense wind slap that broke on the rolling slope of the ridge line, the crown was approximately 2-4 feet deep, average 3 foot, the slide was approximately 75 feet wide and ran almost the length of the entire slope (500+ feet). The wind slab failed on weak layers at the surface and the avalanche broke all the way to the ground.