Avalanche Advisory for 2016-03-12 07:06:24

A March 11th (yesterday) sojourn up to about 9,000 feet on the south side of Mt Shasta gave way to much better snow conditions compared to the wet cascade chunder of the day prior. Temperatures were already a few degrees cooler yesterday morning and dropped further as the day progressed and the cold front pushed into the area. Snow levels started near 6,000 feet but dropped to about 5,000 feet later in the day. Wet snow was still the standard below 7,500 feet, however conditions changed for the better above that elevation. About 6-9 inches of dryer snow was found in most areas due to light wind speeds. Another 6 inches fell last night. Overall, since last Sunday, March 6th, 44 inches of snow has fallen for a storm total thus far of almost 4 feet! And now...another several feet of snow forecast for today through Monday with, FINALLY, some cooler temps to keep things real in our winter playground. Total height of snow at treeline for the 2015/16 winter is 154 inches.

By golly with all the rapid accumulation of snow we've had at times over the week, you would think we would have seen a few more slides other than the Casaval and East side events early on. Visibility has been a big part of the issue...near and above treeline where we'd expect much of the action...one hasn't been able to see much farther than a 1/4 mile at best, thus limiting safe travel. That doesn't mean we haven't been out digging like a dog, looking for instabilities.

With discussion from cohorts, it's thought that due to the warm nature of the storms over the week with short periods of sun and/or rise in temperatures, the snowpack is simply adjusting quickly and settling out very well, almost as it falls. The heavy, wet and sticky snow is bonding to old surfaces, crusts and to itself. Snow pit stability tests and all other observations have not revealed any glaring, unstable results. The warm nature of the snow storms and sun in between has kept it all glued together, essentially. This does not mean that it's all good to go, however. We can double what new snow we've already received over the week... in the next three days. We're not out of the danger zone yet.

Getting into the dirt of it- Yesterday I dug a pit at 8,100 feet on a southeast aspect/25 degree slope in the Old Ski Bowl area, near treeline. Storm total, new snow since 3/6 was 112cm. The sky was completely obscured, it was lightly snowing with light, gusty winds out of the south/southwest. Air temp: 31 F. We have a right side up snowpack hosting two main crusts with one finger to four finger density hardness snow in between the two crusts. The lower crust, the March 7th crust I've mentioned in past advisories this week, is widespread and quite strong. I don't see any weak layers propagating below this crust. The second crust, occurring on March 10th, is much softer (one finger), sits in the upper portion of the snowpack, and is/was moist snow, partially frozen. Stability tests resulted in not much... multiple compression tests 15-20 @ 88 and 47cm up from the old snow. (The OLD snow is very easily discernable by the way. Just dig, you'll find it.) Extended column tests gave way to ECTN/X 20-30 at 88cm up from old snow. The leading weak layer with all tests was just above the newest March 10th crust layer. Shear and fracture quality were moderate to poor. I did note a nice layer of graupel just above the March 7th crust...something to note as graupel can be a decent weak layer. 

Today, all avalanche prone slopes with ample new snow, wind loaded leeward ridge lines, cornices...it should all be suspect. Weaknesses in the snowpack could lie within the new snow from today and tomorrow, OR could step down into the "old" snow layers from the past week. 

The snow will pile up quickly, perhaps several inches an hour. The snow pack does not like rapid change! Existing wind slabs will continue to build in size with steady precipitation expected today. Southerly winds will load NW-N-NE-E-SE slopes. Subtle changes in temperature and snow levels will create different density snow layering. It's often that these density changes act as the weak layer. Your 'A" game is going to be necessary and it might just be a good idea to stay off avalanche terrain entirely. Periods/pockets of HIGH avalanche danger are possible immediately during or just after these storms.

LEFT: Can you see the snow depth sensor? Old Ski Bowl weather station. The snow depth sensor is about 20 feet off the ground! Not buried yet, but getting close! If you're snowmobiling or skiing near it, please do not ride below the sensor. Thanks!

RIGHT: This is how the visibility has been for much of the week near and above treeline on Mt Shasta. This shot taken from the lower ramparts of the Old Ski Bowl, near the weather station.

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LOCAL AREA ROAD, NORDIC, AND SNOWMOBILE PARK STATUS:

The Sand Flat cross country ski trails are in good shape and ready for your cross country skis and snow shoes.  These are backcountry routes marked with blue diamonds on trees.  Trails are not groomed.  Snow shoers, please blaze a parallel trail to cross country skiers staying out of the skin track.  These trails can be accessed via the Everett Memorial Highway.  Thank you, and enjoy!

The Mt. Shasta Nordic Center is open! These beautiful, groomed trails can be accessed via the Ski Park Highway. http://www.mtshastanordic.org

The Pilgrim Creek & Deer Mountain Snowmobile Parks are open!  Trails have not been groomed in the past week and a half due to warm temperatures.  Head to our "Education" tab on our website and find the snowmobile section for trail information, grooming status, and other sledder resources.

The Castle Lake Road is CLOSED at the gate. The culvert blew out and we do not know when it will be repaired. The Everett Memorial Highway is plowed to Bunny Flat.

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