Quick report
- Cracking
- specific
Today, Nick and I returned to Gray Butte to further investigate the natural avalanche estimated to have occurred on Sunday (3/16).
This avalanche is a great example of a persistent slab avalanche:
- Failed on the March 11th graupel layer
- Excellent propagation, stitching between trees, rock outcroppings and mid-slope in uncommon terrain
- Two to three foot average depth, with areas as much as four feet
So, now the question is: Is this layer still a problem to be concerned about?
Consider it a “low likelihood, high consequence” situation. This graupel layer exists all across Gray Butte, only having failed in one location. It's also buried up to 140 cm deep, making it quite hard to trigger. Upon Deep Tap Test, failure occurred on tap 23 (SP), similar to last week's results, suggesting that the layer has not healed much. If triggered, this slab would be very deep, large, and run into a terrain trap. I personally am steering clear of the steep slopes on Gray Butte for a little while longer, until the layer has had time to heal.
All that being said, in the last few days, no shooting cracks, collapsing, or other persistent slab avalanches have been observed.
On a different note, we also found four to six inches of fresh snow, and small wind drifts on E-NE-N aspects.
Observed instability was primarily associated with wind drifted snow. Six to ten inch wind drifts were found on E-NE-N aspects, with localized cracking and small slab releases. The overnight snowfall (4–6 inches) showed no signs of instability. As noted in the forecast, a natural avalanche is estimated to have ooccured on Sunday (3/16) on the NW face of Gray Butte. Upon further investigation, this was a persistent slab avalanche that occured on the buried March 11th graupel layer. This layer is still weak and reactive in the Gray Butte area. Upon Deep Tap Test, the layer failed on tap 23 (SP). As of today, the layer is now 140 cm beneath the surface.Weather
- Air Temp
- 26
- Cloud Cover
- overcast
- Wind Loading
- light
- Rain Elevation
- 3,000
- Recent Snowfall
- 10-15
- Snow Avail For Transport
- moderate amounts
High level clouds kept the skies gray and obscured throughout the day. Mount Shasta was mostly clear of low level cloud cover except for the lenticular clouds above 11,000 feet. No precipitation fell during the day. Light wind blew out of the west, with occasional stronger gusts.
Snowpack
Last night's snowfall provided four to six inches of new snow across the Gray Butte area. Below the new snow is over four feet of snow from the last nine days. The snowpack is consolidating well, with a general right-side-up snow structure.