Avalanche Advisory for 2015-02-08 07:02:13

A quick recap of the storm series that began Thursday (2.5.15) evening... a very impressive wet and windy storm fell on the Mt Shasta area... the first wave provided 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 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 have been as high as 8,500 feet.

Fluctuating temps did some funky things to the snowpack yesterday...  High avalanche danger, powdery dreams and the snowpack were all squished by a rapid warming in temperature that consolidated the snowpack several inches, and lowered the avalanche danger by the end of the day on all aspects below and near treeline. Temps cooled back down soon after this warm up and created a 2-3cm zipper crust layer that is now overlaying our storm snow. Poor visibility allowed us to make it to only about 8,500 feet in the Old Ski Bowl and this crust layer was still present at that location. It's uncertain at what elevation the crust may disappear.

Avalanche activity above treeline, which was almost certain, probably occured during this warm up albeit out of view for us. The spike in danger has subsided for below and near treeline areas and no natural or human triggered avalanches were observed. Stability tests and observations yesterday revealed good stability for said areas and we saw widespread consolidation and stabilization within the snowpack due to the warmer temps. That said, we were not able to get a view of the upper mountain and uncertainty lingers regarding the avalanche danger above treeline, above the freezing level. Further uncertainty remains as to which layer(s) within the snowpack will be weakest at mid to upper mountain levels.  While we don't sit at high danger any longer, I do believe things could still be touchy above treeline, higher than 8,600 feet. 

Pit profile below on the top shows the snowpack soon after the first storm wave. The second profile on bottom shows the snowpack after our warm up and formation of crust layer(s) and saturated snow within top layers. Poor propagation and poor shear quality was found within weakest layer, just below saturdated, wet snow.

The bottom line synopsis: Below and near treeline areas.... the avalanche danger has dropped considerably from warm up/cool down. Areas above treeline remain uncertain and considerable avalanche danger could be found. Weak layers may exist within Friday/Saturdays wind and storm slabs, or form within new/expected snow. Today, visibility will remain poor and more snow and southwest wind are forecasted with cooling temps. While this is welcomed by all powder hounds alike and will hopefully put a nice light density, snowy finish to our weekend storm series, we will continue to see potentially dangerous avalanche conditions above 8,600 feet on slopes steeper than 30 degrees. Cornices and wind loaded starting zones should be avoided for the next several days.

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.

-------------------------------------------------------------------------------------------------------------------------------

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.