Avalanche Advisory for 2014-12-13 06:59:48

The storm that began on Wednesday the 10th of December gave the Mt Shasta area a large dollup of new snow that came in mostly "right side up". That is, heavier snow on the bottom and lighter snow on the top. We like that. However, that being said, as much as 4 feet of snow fell in 48 hours and was accompanied with moderate, southwest winds...a red flag. Wind slabs and storm slabs are the avalanche problems of most concern currently.

Backcountry skiers yesterday came across some impressive debris of a large natural avalanche (HS-N-D3/4-R3/4) that slid down Avalanche Gulch proper and ran past the Horse Camp (Sierra Club) cabin. The avalanche likely occured on 12/11/14. Visibility was poor so knowbody got a good view of the starting zone and/or full extent of this slide. The avalanche came down through Avalanche Gulch proper, and not the "climbers gully". Thus, the starting zone was likely the Sargents Ridge, Thumb, Redbanks area. This slide is a good reminder of the potential for large avalanches on Mt Shasta during heavy winter storms. Slides like this can easily extend into runout zones on relatively flat terrain...ground that one might travel on and think they are not in avalanche terrain. Always know what slopes are above you and travel with caution even when below treeline. You may be in a runout zone. 

I got a glimpse of the Old Ski Bowl yesterday and thought maybe I would see another large slide in the bowl, however the slopes remained intact. Today I remain a bit nervous: Its the weekend with clear skies forecasted....large wind and storm slabs still lingering...folks chomping at the bit to get perfect, untracked powder. Let's take all this into consideration.

While snow stability seemed good in below and near treeline areas, I continue to have concern for above treeline slopes today. Yesterday at 8,300 feet in the Old Ski Bowl, I was able to repeatedly get moderate failures 70cm down from the top of the snowpack with compression and extended column tests. Clean, quality 1 and 2 fractures were initiated with both tests at a density change in the snow, though full propagation did not occur with extended column tests. These tests were performed on an East facing slope, 30 degrees. At this pit location, 95cm of new snow was recorded. The top layers of snow measured in at 14-15% water content while the bottom layers of new snow came in at 15-16%. While full slope propagation might be difficult, a heavy, high marking snowmobile or skier on a very deep and unstable wind slab could create disaster.

Shooting cracks were observed by a couple local skiers near treeline on Green Butte Ridge yesterday.

Overall, folks have been able to find some great, safe, early season skiing at below and near treeline areas. It is advised to still stick to lower angle slopes for another few days and give runout zones plenty of room.

Three photos below: Avalanche Gulch slide.  Photos taken on 12/12/14. Slide occured sometime likely on 12/11/14

Photo: Chris Carr

Photo: Chris Carr

Photo: Angela Towner

Report your observations to the MSAC! A photo, a few words... send them in! (nimeyers@fs.fed.us or 530-926-9614)

Castle Lake area still has no snow.

Mt Eddy area is hosting about a 18" of snow. I have not been up into that area yet and have received no reports.

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Terrain:  Remember most of the terrain that we like to play on is greater than 30 degrees.  Avalanches are possible on anything steeper than 30 degrees.  Avoid cornices, rock bands, terrain traps and runout zones of avalanche paths.

Weather:  Most of our areas avalanche danger will occur 24-48 hours after a storm. We still can see persistent weak layers from time to time and we always will be sure to let you know about that!  Heed the basic signs: Wind (significant snow transport and depositions), Temperature (rain/snow/rain/snow, which in turn weakens the snowpack), and Precipitation (Snow or rain add weight and stress to the current snowpack).

Snowpack:  If snow accumulates, give the snowpack a chance to adjust to the new snow load before you play on or near steep slopes (greater than 30 degrees).  Most direct action avalanches occur within 24-48 hours of recent snowfall.  Watch for obvious signs of snowpack instability such as recent natural avalanche activity, collapsing of the snowpack (often associated with a “whumphing” sound), and shooting cracks. If you see these signs of instability, limit your recreation to lower angle slopes.

Human Factor: Don’t forget to carry and know how to use avalanche rescue gear. You should NOT be skiing or climbing potential avalanche slopes without having beacons, shovels, and probes.  Only one person in a group should be exposed to potential avalanche danger at a time.  Remember, climbing, skiing, and riding down the edge of slopes is safer than being in the center.  Just because another person is on a slope doesn’t mean that it is safe.  Be an individual!  Make your own decisions.  Heed the signs of instability: rapid warming, “whumphing” noises, shooting cracks, snowing an inch an hour or more, rain, roller balls, wind loading, recent avalanche activity.

The Five Red Flags of Avalanche Danger any time of year include:  1) Recent/current avalanche activity  2) Whumpfing sounds or shooting cracks  3) Recent/current heavy snowfall  4) Strong winds transporting snow  5) Rapid warming or rain on snow.