Avalanche Advisory for 2016-03-10 07:13:18

Despite mist, fog and very poor visibility yesterday, I traveled up into treeline areas on the south side of Mt Shasta for a look at the snowpack. With the recent new snow, sun, rain and mixed weather we've had over the past three days, I figured there might be a few layers of concern...especially given the looming forecast for additional FEET of snow. I am a little uncertain how exactly the current snowpack will accept the ample amounts of new snow over the remainder of the week, but my gut feeling is that we will see some avalanche activity. That said, we've had three days for the snow to settle out. Upwards of 8-10 inches of settlement occured in some areas and the only avalanches we observed or have been reported are the Casaval and East side slides, both SE facing slopes at similar elevations, occuring late on 3-6 or early on 3-7. Above treeline is still uncertain from lack of snowpit data. My biggest concern is not so much the current snowpack as it stands, but ample amounts of NEW snow ON TOP of our current snowpack in the coming days.

The current snowpack, above the hard, old snow, consists of approximately 50-55cm new snow near treeline. Most of that fell over the course of 15 hours this past Sunday/Monday (3-6 and 3-7). It was mid to late in the day on Monday the 7th that our temperature/sun crust formed and froze, creating a 1-2cm pencil hardness zipper crust. This crust lies about 10-15 cm deep in the snowpack. The crust distribution is fairly widespread and can be easily felt with hand pits, though in some areas immediately adjacent, the crust was absent. This was in part due to shading from trees and/or a shadier aspects. Northerly aspects, the crust is absent. On top of the crust, 10cm of snow fell most recently early in the week and another few inches on top of that from the last 24 hours. Late yesterday, despite an air temperature of 31 degrees, a light mist/rain was present at 8,100 feet and was creating a very thin rain crust on the immediate surface of the snowpack. So...that is the current set-up.

Stability test wise, weaknesses were consistent directly below the March 7th sun crust, but propagation was poor. [ ECTN18@37cm - Q3 / CT4@35cm - Q3 / PST30/100(SF) down 13cm ] Lighter density snow exists below the March 7th crust and this was the failing layer with all tests. It is my concern that rapid onset of heavy precipitation, high precip rates including rain on snow, additional wind loading...all these factors on top of this snowpack could create small to large slides in the coming days. Additionally, the thin rain crust of mention on the surface of the snowpack could create a suttle enough bed surface for another potential weak layer.

Above treeline observations have been limited due to visibility. We got a good look at the southeast facing slide off Casaval Ridge and the East side on Monday. Remaining and also NEW wind slabs above treeline are certainly a possibility today and for the rest of the week. Below treeline, rain on snow yesterday helped squish the snowpack and avalanche concerns are minimal, again below treeline.

Today, wind loaded slopes above treeline will be the biggest concern. Existing wind slabs will continue to build in size with steady precipitation expected today. Southerly winds will load NW-N-NE-E-SE slopes. 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 of HIGH avalanche danger are likely immediately during or just after these storms.

Left - March 7th crust, 1-2cm thick sitting 10-15cm deep in the snowpack, now deeper due to 8 inches new snow within the last 24 hours. Right - New snow since Sunday the 6th.

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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.