Loose wet avalanche activity will occur this spring and involves the release of wet unconsolidated snow or slush. Usually this type of instability forms in response to daytime warming within the layers of the wet snow near the surface of the snowpack. They often start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. They generally move slowly, but can contain enough mass to cause significant damage to human life and limb. You can use the Old Ski Bowl and Gray Butte weather stations to monitor overnight and daytime temperatures. Cloudy skies overnight and air temperatures above freezing do not allow the snowpack to refreeze very well. When the snowpack does not refreeze overnight, travel on steep slopes should be avoided. Under clear skies, the top few inches of the snowpack will often regreeze despite near or slightly above freezing air temperatures. This superficial refreeze allows for a short period of good travel conditions in the early morning hours before surface wet snow instability becomes a concern. If a solid overnight refreeze occurs, getting out early and finishing mid-day is best. Your travel should start with east aspects and follow the sun around to north aspects. Get off your equipment and check boot penetration depth. Boot-top deep, wet snow, significant roller ball activity, or any loose wet avalanche results from small test slopes all indicate wet snow instabilities can occur. Moving to a different aspect with less sun exposure or terrain less than 30 degrees slope angle without steeper terrain above.
Natural and human triggered wind slab avalanches may occur during and immediately after any late season storm. Wind slabs are often smooth and rounded and sometimes hollow, and can range from soft to hard. Expect a period of snowpack instability during the storm, then potentially a second cycle of avalanche activity as rapid warming occurs post storm. During the storm, watch for typical signs of mid winter instability such as recent avalanche activity, wind loading, collapse, audible whumphing sounds, and/or shooting cracks. Post storm, new snow will be very sensitive to rapid warming and direct sunlight. Pay close attention to layer bonding within the new snow and to the old snow surface beneath. It can loose strength rapidly as the day progresses causing a significant increase in avalanche danger.
Avoid avalanche terrain with recent wind deposits or choose slopes gentler than 30 degrees in steepness. Always pay attention to terrain above you as well. Wind slabs tend to stabilize within a few days unless deposited on a persistent weak layer.
During periods of rapid warming after new late season snowfall, storm slabs and wind slabs can transition to wet slabs. The high angle sun in late April and May allows for more incoming solar radiation to affect the snowpack than what occurs during the winter months. If a weak layer sits below the newly formed slab, rapid warming can deform the new slab and add weight to the weak layer below. In some cases, natural and certainly human triggered wet slabs during periods of rapid warming can occur. Wet slabs involve the release of a cohesive layer of snow (slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below. They can occur during warming events and/or rain-on-snow events. Wet slabs can be very destructive. As conditions may be affected by sun, rain, or warm temps, choose slopes gentler than 30 degrees in steepness with nothing steeper above. Timing before the onset of significant sun/warmth is key.
The Mt Shasta area has finished off winter with precipitation (since October 1st, the beginning of the wet season) at 32.77 inches of water, normal is 36.68, which puts us as 89% of normal. For 2015, we sit with 13.25 inches of water, normal is 21.47, or 61% of normal. Snow survey for the Sacramento, Shasta and Trinity Watersheds is far below normal for the month of April. Snowpack for the Mt Shasta area is 24% of normal with water content at 26% of normal. Even more concerning is the McCloud area snowpack. There is no measureable snow. For the first time since 1945, the first year snow surveys were started on the McCloud river watershed, McCloud courses were 0% of normal. The majority of Southern Siskiyou Counties current snowpack exists above 7,000 feet in elevation. Snowpack above this elevation actually shows a favorable increase from last year. However, after entering the fourth year of below average snowpack and no current snowpack in the lower elevations, the drought will have serious implications to water supplies and on the health of natural resources and wildlife.
For more information and data both current and historical, here are some resources:
1. Natural Resources Conservation Service: http://www.wcc.nrcs.usda.gov/
2. California Snow Water Content graphs: http://cdec.water.ca.gov/cgi-progs/snow/PLOT_SWC
3. California Snow Water Equivalent Summary: http://cdec.water.ca.gov/cdecapp/snowapp/sweq.action
4. California Climate Tracker: http://www.wrcc.dri.edu/monitor/cal-mon/
5. Climate change and California drought in the 21st century by Michael E. Mann and Peter H Gleick http://www.meteo.psu.edu/holocene/public_html/Mann/articles/articles/MannGleickPNAS2015.pdf
6. Anthropogenic warming has increased drought risk in California by Noah S. Diffenbaugh, Daniel L. Swain, and Danielle Touma: http://www.pnas.org/content/112/13/3931.full.pdf
Always remember the five red flags of avalanche danger (see below). Other hazards on Mt Shasta such as cornice collapse, moats, thin snow bridges over crevasses, glide cracks, shallow buried rocks, and exposed creeks exist. Please check the CLIMBING ADVISORY for the latest climbing information, trailhead status and other good info. Please note that the summit pass (required for climbing anywhere above 10,000 feet) is now $25 dollars.
Thanks for the continued support, photos, trip reports and backcountry observations! Support from the National Forest Service and private sponsors as well as individual donors make this program financially possible. As the seasons begin to change, the morning air becomes crisp and the days become shorter, check back on our home page for fundraising and event dates for the 2015-2016 season. Have a great summer and we will do it all over again here next fall!
Report your observations and feedback to the MSAC! A photo, a few words... send it in! (firstname.lastname@example.org or 530-926-9614)
Sand Flat Winter Trails: CLOSED
Pilgrim Creek Snowmobile Park: CLOSED
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’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.
|0600 temperature:||deg. F.|
|Max. temperature in the last 24 hours:||deg. F.|
|Average wind direction during the last 24 hours:|
|Average wind speed during the last 24 hours:||mph|
|Maximum wind gust in the last 24 hours:||mph|
|New snowfall in the last 24 hours:||inches|
|Total snow depth:||inches|
For current weather conditions in Mt Shasta City: http://raws.wrh.noaa.gov/cgi-bin/roman/meso_base.cgi?stn=KMHS
WEATHER STATION INFORMATION (0500hrs): Current weather station information is availabe on our website under the WEATHER tab, or click the Meso-West links below.
On Mt Shasta (South Side) in the last 24 hours...
Old Ski Bowl - 7,600 feet, http://raws.wrh.noaa.gov/cgi-bin/roman/meso_base.cgi?stn=MSSKI
Gray Butte - 8,000 feet, http://raws.wrh.noaa.gov/cgi-bin/roman/meso_base.cgi?stn=MSGRB
Castle Lake and Mt Eddy (West side of Interstate-5)...
Castle Lake - 5,600 feet, http://raws.wrh.noaa.gov/cgi-bin/roman/meso_base.cgi?stn=MSCAS
Mt Eddy - 6,500 feet, http://raws.wrh.noaa.gov/cgi-bin/roman/meso_base.cgi?stn=MSMED
Always check the weather before you attempt to climb Mt Shasta. Further, monitor the weather as you climb. Becoming caught on the mountain in any type of weather can compromise life and limb. Be prepared.