Avalanche Advisory for 2015-02-07 07:05:07

Locals were getting uncomfortably comfortable with the easy, post ski boot-to-flip flop transition at trailheads over the month of January, soon followed by the familiar sounds of "thwack" (lawn chair unfolding) and "ka-boosh" (beverage of choice) in the Bunny Flat parking lot. My, how this has changed... one has to actually wear snow boots and use 4wd to the trailhead now!

Enough tongue and cheek. Beginning Thursday (2.5.15) evening, a very impressive wet and windy storm fell upon the Mt Shasta area. This first wave of this weekends storm series dropped 33.5 inches of snow (5.38 inches water) over 36 hours, recorded at 7,600 feet on the south side of Mt Shasta (Old Ski Bowl weather station). Winds have averaged 20-30 mph, southeast to southwest with gusts into the 40's and 50's, recorded at the Gray Butte weather station, 8,000 feet, also on the south side of Shasta. Snow levels fell as low as 5,000 feet during the beginning of the storm, but most of the snow was above 6,000 and snow levels rose to near 7,000 feet by yesterday afternoon.

My partner and I choose a safe route up Green Butte Ridge yesterday and took our time digging several hand pits along the way, skinning across many small test slopes and stomping on small corniced areas. Immediately we were able to get easy triggered wind slabs and cornice drops. This was not all that surprising given the conditions, however eye brow raising since we've had such a lack of avalance activity for over a month! We ended our ascent at 8,200 feet on GB Ridge (treeline) due to lack of visibility and honking winds. Wind loading was obvious on southwest, west, northwest and northerly aspects. A full pit was dug on a west/southwest aspect below the ridge top and multiple stability tests resulted in easy to moderate failures within the new storm snow. A total of 85cm of new snow was recorded on top of the old snow surface. A couple extended column and compression tests gave us an ECTP16@20cm from bottom, ECTN17@35cm, and CT12@40cm. The jist of our tests found easy to moderate failures in new storm snow at a density change within snow layers at 20 to 40 cm up from old/new snow interface. Another group of local observers recorded almost exactly the same results on a similar elevation, south/southwest facing slope. This denisty change in the snow was likely due to a brief decrease in wind during the storm. 

With the given conditions that have been observed since the onset of this storm, temperatures warming yesterday afternoon/this morning, high intensity snow accumulation, wind... potentially dangerous avalanche conditions will exist today near and above treeline on Mt Shasta. Further, slopes steeper than 35 degrees below treeline could also host pockets of dangerous avalanche conditions. Play it safe today and for that matter, for the next several days as more rain, snow and wind persist. Terrain selection is paramount. We are expected to get more snow and more wind this weekend, all lending toward increased load on the already stressed snowpack. If small to large slides have not already occured, they could be ripe for triggering by a skier or snowmobiler in the next couple days.

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The Mt Shasta Avalanche Center has issued an AVALANCHE WATCH for the forecast area, in effect Friday 8am PDT through Saturday 8pm PDT.

The Mt Shasta area is forecasted to receive between 6 to 10 inches of water by Monday evening, which could mean 6-8 feet of snow near and above treeline on Mt Shasta. Snow levels will fluctuate between 6,000 and 8,000 feet. Extremely strong, south/southwest winds will accompany this storm which will predominantly load north and east slopes with deep snow. Concerns for small to increasingly large wind and storm slab avalanches exists for all aspects, near and above treeline on Mt Shasta this weekend. 

Avalanches from the upper mountain may become large enough to impact lower elevation avalanche runout zones. Avoid travel in low angle runout zones below treeline.

Those traveling on Mt Shasta this weekend should have extensive avalanche knowledge and use careful route selection. Always travel with a partner and carry an avalanche beacon, shovel and probe... and know how to use them.
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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 has a shallow snowpack. Be careful of shallow buried objects. Skiing has been reported as poor to non-existent.

Sand Flat Winter Trails: OPEN, trail conditions are firm and getting thin with some tree debris on snow surface. 

Pilgrim Creek Snowmobile Park: OPEN, however due to lack of low elevation snow, one must drive up the road several miles before enough snow is encountered. One CANNOT DRIVE over Military Pass.

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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.