Avalanche: Summit

Location: Fresno

Date:
Observer:
Route & General Observations

Ascended an east facing sub-ridge of Fresno to the main ridge and traveled up to 3900′ to look into start zones. Descended near our uptrack. Variable surface conditions—none that were particularly pleasant skiing. Beautiful day!

Avalanche Details
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Trigger NaturalAvalanche Type Soft Slab
Aspect NortheastElevation 3500ft
Slope AngleunknownCrown Depthunknown
WidthunknownVertical Rununknown
Avalanche Details

Natural avalanche on Fresno likely occurred Monday during WNW wind event

Red Flags
Red flags are simple visual clues that are a sign of potential avalanche danger. Please record any sign of red flags below.
Obvious signs of instability
Recent Avalanches?Yes
Collapsing (Whumphing)?No
Cracking (Shooting cracks)?No
Observer Comments

Multiple avalanches that likely occurred the day before during the WNW winds Sunday night and Monday
We observed slab avalanches on Moose Mt, Tri-Tip, Butch, Fresno, Summit Peak, Silvertip shoulder, Wolverine, and Tincan (maybe just a loose snow avalanche? I could not see the crown). Most avalanches had a northern or slightly northern tilt to the start zone that released. We wondering if the more westerly winds were getting channeled from the south along hwy corridor similar to the way it happens in Turnagain Pass and then loading north facing start zones.

Wind transport observed - wind increased in the afternoon
Localized cracking on wind loaded pockets

Weather & Snow Characteristics
Please provide details to help us determine the weather and snowpack during the time this observation took place.
Weather

Clear
Temperatures 4° while taking pictures near Summit Lake, teens while touring
Winds were WNW 5-15 gusts into the 20s

Snow surface

Variable
Very thin melt-freeze crust with wind textured on top of facets over a more supportable crust on solar aspects.
Breakable wind crust over a few inches of cold snow over more wind hardened snow or wind blow to no ski pen wind hardened surface on northerlies. Dense drifts and lots of wind texturing.

Snowpack

Loose facets under wind crust/slab while skinning and booting on east ridge
We dug one pit at 3700' on an east aspect, 20° slope. HS: 130 cm, dug to ground. There was a 1F wind compacted layer that was 1.5-15 cm deep (variable wind loading) over small facets and decomposing stellars CT12 (15 cm) down, CT4, CT5, ECTP17 (4 cm down), 35 cm down there was chaining small facets (.5-1 mm) over a decomposing melt-freeze crust, ECTP23 (x2), ECTP18, ECTX. 78 cm down there was another layer of chaining facets(.5-1.5mm), no test results. The basal facets (1-3 mm) are dry and loose. Where we found them over rocks they were slightly more defined compared with a deeper spot (160 cm) over heather where they showed more rounding. One of our focused questions were looking at where water will pool when/if we ever get a true warm up and looking at structure that could be somewhat similar to the avalanches on Summit Peak.

Photos & Video
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