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Observations

Region: Anchorage Front Range
Location: Gordon Lyon / Arctic Valley
Observer:
Date:

Route & General Observations

Toured up the valley between Gordon Lyon and Arctic Valley. Skinned and skied the E aspect above the tubing hill / parking lot. LOTS of whumphing and cracking around skis. Very shallow snowpack in this spot, hit some rocks. Then headed up valley towards the Gordon Lyon – Rendezvous saddle. Decided to head up the slope directly E of the radar site, because it looked much more appealing to be in the sun. Didn’t get very far due to MASSIVE shooting cracks and continuous whumphing.

Red Flags

Obvious signs of instability

Recent Avalanches?NoCollapsing (Whumphing)?YesCracking (Shooting cracks)?Yes

Observer Comments

WHOA!

First run up E aspect above the tubing hill / parking lot, got continuous whumphing and cracking around skis.

Then headed up valley toward the Gordon Lyon-Rendezvous saddle, but then decided to head up the slope directly E of the radar site, because it looked appealing to be in the sun. As soon as we started working our way up the S ridge of the slope, I got a huge whumph followed by MASSIVE shooting cracks at about 3200 ft. The cracks went for 30-40 meters, wrapping around a corner. The crack did not originate from my ski tips, it cracked about 15 meters above me and about 10 meters below me (i.e. where the crown and stauchwall would be if it had slid). See photos. Dug into the shooting crack, the crack went down to the basal facets in the vegetation.

Traveled about another 50 meters, got another new set of 30-40 meter shooting cracks.

Turned around, got another new set of 30-40 meter shooting cracks.

While skinning back down valley, we observed a skier at Arctic Valley plunge into the creek gully, sending out massive shooting cracks behind him. Also saw another spot where a skier at Arctic Valley triggered shooting cracks on the creek wall while traversing above it. Neither slope slid.

Unable to produce any avalanches on small test slopes, just storm snow sluffing.

Weather

Weather

Clear to scattered clouds. Calm to light wind from the E. -6.5C @ 11:30 AM. HST = 25cm.

Snow Characteristics

Snow surface

HST = 20-25cm. Very low density! Skiers at Arctic Valley were sending up huge rooster tails. Visible wind effect on SE aspects.

Snowpack

Depths are extremely variable, ranging from HS=~30 cm to ~100cm. General structure is F-4F snow from the last couple of storms, over 1F-P hard wind slab, over 4F-F hard basal facets (completely rotten sugar snow).

Dug a pit on a SSE aspect @ 2900 ft elevation. HS=95cm. Got CT17 SC down 65cm on basal facets, ECTN3 down 25cm (storm snow), ECTN6 down 35 cm (new snow on top of 1 F wind slab), ECTP26 SC down 70cm on 2-3mm basal facets.

Bisected shooting cracks to see failure layer. In all cases shooting cracks went down to 2-3 mm basal facets in vegetation. Starting to see well developed cupping and striations in basal facets.

Some hand pits failed on isolation, at the basal facets. All were otherwise easy failures. Pole probing revealed an extremely spatially variable snowpack, with varying degrees of wind slab in the mid pack.

Forecaster Comments

Forecaster Comments

It turns out, an Arctic Valley snow safety worker saw the party at their high point up the East valley. The party remotely triggered a small 25' wide pocket (D1) that was out of sight from the party. Debris piled up in the gully below, no photos.

Photos & Video

Photos



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