Loose wet avalanche on Tinemaha

AVALANCHE OBSERVATION
Tinemaha East Face
Submission Info
Forecaster
Saturday, April 13, 2019 - 12:45pm
Avalanche Type: 
Wet
Slope: 
40degrees
Trigger type: 
Unknown
Aspect: 
East
Terrain: 
Above Treeline
Elevation: 
12 450ft.
Avalanche Length: 
3 100ft.
Number of partial burials: 
0
Number of full burials: 
0
More detailed information about the avalanche: 

Posted on behalf of Dan Chirpich, thanks Dan for all the info!  

At 12:45pm, a wet loose slide ran 3100' down the main ski route on the east face of Mt. Tinemaha.  It ran from the SE extent of the summit ridge where a solo skier was seen booting across stepp terrain roughly 50 feetish down slope of the ridge.  We are unsure if he set if off, but one of his skis was washed downhill over 1500'.  The slide ran 3100' down over 2500' of the gut of the ideal ski descent and stopped at 9300'.  The skier declined to respond to our loud communication, but he yelled he lost his ski.  I went and stood it up veritcal since it was just across the slope form me.  He then knocked a boulder the size of my torso down the slope, and to his credit yelled rock as loudly as possible many times.  The Slide wasn't big enough to bury someone wihtout a terrain trap, but it certainly would have pulled an unaware skier down.  The slide seemed likely to be only ~5cm of surface snow getting entrained, but it did clean off a 50'+ wide swath.  It cut 25cm deep in one spot low down.  All my numbers except the length of the slide are estimated.  

Conditions going up were FAR more locked up and forzen than my prior report on many paths slding on Tinemaha on the 8th when clouds overnight and warm temps kept the slope from getting more than a superficial freeze.  slope was warming to yield ankle deep penetration up until we topped out at noon. There was variable pockets of new snow no more than 15ish cm deep on ascent.  After enjoying a beautiful scenic summit for 30min, we were making turns down on surprising granular surface snow that was reasonably supportive.  One or two turns set off a lazy sheet that cleaned a bit of surface snow and ran for maybe 40', but most of the slope we were skiing wasn't steep enough for the debris to gain momentum.  Some pinwheeling off turns, but there was a surprisingly supportive base that provided very enjoyable skiing.  The skiing was infinitely better than when we turned around at 10.8k at 11:30 on the 8th.  

Given the conditions we experienced, my best guess is that the slide originated from steep (45°+?) terrain around where the guy was traversing.  Im guessing the slide gained momentum on the steep slope and then simply managed to entrain enough other snow to make it run as far as it did.  We weren't seeing other naturals, so we suspect the solo skier triggered it.  

Avalanche Photos: 
Precipitation: 
None
More detailed information about the weather: 

Clear skies overnight and all day.  Freeze felt bomber until 9-10am.

Number of People Caught: 
0
37° 2' 11.2884" N, 118° 23' 41.8632" W

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