| Recent Avalanches? | Yes |
| Collapsing (Whumphing)? | No |
| Cracking (Shooting cracks)? | No |
Observation: Turnagain
Location: Silvertip
We toured up Silvertip Creek to investigate a very large natural avalanche that released sometime after the Dec.19th storm. Debris was found along the valley floor and the crown spanned just under 2 miles. The debris didn’t have any new snow on it, but it did have +10mm surface hoar covering it. The avalanche likely released at the end of the storm (Dec.19th or 20th) enough time to allow for well developed surface hoar growth. Estimated crown height 2-4′
SS-S-U-R4-D4-G/O
Obvious signs of instability
Observer Comments
Lots of recent natural dry loose snow avalanches "Sluffs" were observed on all aspects on steep terrain.
Weather
Clear skies
10F-15F
West winds 15-20mph
No precip
Snow surface
Lots of well developed surface hoar covering 8-10" of near surface facets. Along ridge above 2000' a West wind (15-20mph) was blowing the surface hoar around, filling in the skin track. The wind blown surface hoar and facets made the skin track very slippery.
The top 8-10" of snow is faceting out, becoming poorly bonded near surface facets. Lots of recent natural loose avalanches were observed on all aspects in steep terrain.
Snowpack
Dug two test pits with no significant results.
Pit 1- 2500' HS=130cm, N aspect,Test Results: ECTX x 2. Found two crust layers, Thanksgiving crust layer in a similar location as Pit 2, 30cm above the ground. Another crust was found at 90cm. Pit was very uniform in hardness gradually increasing from Pencil hard 1F hard at 40cm to 105cm. Top 25cm of snow was Fist hard Near surface facets. Surface hoar (6mm) was partially intact, but wind was stating to blow them over.
Pit 2- 3100' HS=100cm, N aspect, Test Results: ECTN20, ECTN30 - Q3 failed at a slight density change about 13" below the surface. No propagation potential was found, but did find Thanksgiving crust 30cm above the ground with rounding facets on top. Basal facets were rounding on the ground, but still identifiable (2mm) See pit diagram for details.
Debris in Silvertip Creek and valley floor. Evidence of powder blast was observed several hundred feet on opposite side of creek.
A very long and connected crown on ENE aspect of Twin Peaks ridge above Silvertip Creek. Spans just under 2 miles.
Far Southern side of crown on Twin Peaks ridge
Far Northern side of crown on Twin Peaks. Could see pockets where the avalanche stepped down to the ground.
Surface hoar growth (10mm in size) on a small piece of debris that was blasted to opposite side of drainage.
Dry loose 'sluffs" observed on a Western aspect in the Silvertip drainage.
Pit 2 at 3100' on Silvertip.
Across the Seward Hwy on a SW aspect several smaller D1.5 slabs were seen in good light in three seperate gullies.
Screen Shot 2015-12-23 at 7.35.30 PM
Picture of snow blasted to opposite side of creek. Thanks Jack for the pic!