Soft Wind Slabs, San Joaquin Ridge

Submission Info
Friday, February 23, 2018 - 11:00am
Red Flags: 
Whumphing noises, shooting cracks, or collapsing
Recent loading by new snow, wind, or rain
37° 40' 48.36" N, 119° 3' 20.52" W
Snowpit Observations
More detailed information about the snowpack: 

Toured N along San Joaquin Ridge from Minaret Vista, poking into the NE facing bowls on the E side of the ridge looking for wind slab sensitivity and distribution on northerly aspects and for blowing snow from N winds.

Test slope near treeline on NNE facing wind loaded rollover at 9200' in the first bowl past the Vista had small results. Very soft wind slab failed on near surface facets and slide on a buried melt-freeze crust, D1 (see photos of crown and slide). This slab was thick at the crown but became thinner quickly as it extendend down the slope. It didn't reach very far down the slope. Since it was sitting on facets and the temps are going to remain cold, I would expect similar slabs to take longer to stabilize than normal. Stopped at the top of the third bowl up the ridge, the first one with big terrain, to look for natural avalanches. No naturals noted. The terrain in this area is very steep, consists mainly of chutes, had obviously been windloaded (4' tall cornice on N aspects) and is exactly the type of terrain I had decided to avoid today. Got some shooting cracks from my skis as I was skirting around to get a look at the cornice (see photo). Moderate N winds were transporting snow onto the S facing ridge at the top of this bowl (see video) and the soft snow down wind was developing the thinnest softest wind skin by noon. Hand shears along my route had mixed results: those done right in wind drifts failed on isolation while elsewhere they were totally unconsolidated storm snow, in many cases right next to eachother.

Sheltered areas along the ridge had ~30cm of light new snow, areas that had been stripped had ~15cm left over. Some SE facing slopes had wind lips, but kick tests resulted only in sloughing.

Aside from the blowing snow at the third bowl winds were generally calm on San Joaquin Ridge except for occasional periods of light N wind. Sky = Broken.

General impression: there are certainly touchy wind slabs today if you find the specific terrain where they live. In big wind loaded terrain some of these slabs could be touchy and large. I would have expected the problem to be more widespread and bigger if the storm had been a little warmer, the snow a little thicker, and the winds less turbulent and more consistent.

Snowpack photos: 
Snowpit videos (tests, etc): 
Weather Observations
Blowing Snow: 
Air temperature: 
Wind Speed: 
Air temperature trend: 
Wind Direction: 
Accumulation rate: 
More detailed information about the weather: 
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