Avalanche Advisory for 2015-02-14 07:00:11

Sunny skies and mild temperatures are going to make for an enjoyable holiday weekend on the slopes of Mt. Shasta!  After a healthy dollop of new snow from last weekends record setting storms (water, not snow), we have entered a transitional period towards a melt/freeze cycle that started this past Tuesday. We probably don't have to tell you, but... aspect, elevation, and time of day are going to dictated snow quality and condition.  Low to mid elevation south-southeast slopes offer the best chance for daytime softening and prime corn conditions.  Yesterday, good corn snow was present up to at least 10,000 feet and good corn skiing was reported in Avalanche Gulch from Helen Lake down.  The few snowmobilers that were out and about enjoyed the same conditions in Old Ski Bowl.  

The warm daytime temperatures and mild night time lows have helped to consolidate and stabilize the 3-4 feet of new snow from last weekend.  A few avalanches did occur during and immediately after the storms. Debris was barely visible from a good size slide in Avalanche Gulch early in the week. Other slides likely occured, but by the end of the storm cycle evidence of avalanches was scarce.

Currently, confidence is high for increasing snowpack stability.  Yesterday a snow pit was dug on the east aspect of Green Butte at 8,720 feet, in the vicinity of a previous snowmobile triggered slide that occured on 2.12.15.  A couple extended column test resulted in ECTX test scores.  This means that no fracture occurred during the test. (See pit profile below) Snow crystals continue to bond and gain strength due to sunny days and an isothermal snowpack was observed. It seems that the snowmobiler triggered slide failed on the wet, saturdated snow layer within the top 20-30cm of the snowpack. We could not reproduce this failure in tests.

Images:
Pit profiles from last weekend, and yesterday. 
A look into Avalanche Gulch from Casaval Ridge from 2.11.15 - Photo: H Meyers
Snowmobile triggered slide (2.12.15) of the East aspect of Green Butte. Pit location on lookers right flank. - Photo: S Malee

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. The road to Castle Lake is currently CLOSED due to flooding and culvert damage that washed out the road.

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.